Reforming Apparatus and Method

ABSTRACT

A multiple adiabatic bed reforming apparatus and process are disclosed in which stage-wise combustion, in combination with multiple reforming chambers with catalyst, utilize co-flow and cross-flow under laminar flow conditions, to provide a reformer suitable for smaller production situations as well as large scale production. A passive stage by stage fuel distribution network suitable for low pressure fuel is incorporated and the resistances in successive fuel distribution lines control the amount of fuel delivered to each combustion stage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/445,601, filed Apr. 12, 2012, which is a divisional of U.S. patentapplication Ser. No. 12/157,695, filed Jun. 11, 2008, now U.S. Pat. No.8,177,868, which is a continuation-in-part of U.S. patent applicationSer. No. 11/818,916, filed Jun. 16, 2007, now U.S. Pat. No. 7,967,878,which is further a continuation-in-part of U.S. patent application Ser.No. 10/500,176, filed Jan. 10, 2005, now U.S. Pat. No. 7,276,214, whichis the National Stage under 35 U.S.C. §371 of International PatentApplication No. PCT/AU2003/000022, filed Jan. 3, 2003. Each of theforegoing related applications, in their entirety, are incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to apparatuses and methods for reforming ofgaseous hydrocarbons and more particularly relates to high efficiency,low metal dusting, low coking apparatuses and methods for reforminggaseous hydrocarbons.

BACKGROUND OF THE INVENTION

Steam reforming is a catalytic reaction in which a mixture of steam andgaseous hydrocarbons is exposed to a catalyst at high temperature toproduce a mixture of carbon oxides and hydrogen, commonly known assyngas. Syngas may be further converted to a very wide range of bulk andspecialty chemicals, including hydrogen, methanol, ammonia, transportfuels and lubricants.

The chemical reactions involved in steam reforming have been well knownfor many years. Indeed, steam reforming has been used by industry sincethe 1930s, and steam reforming of natural gas has been the dominantmethod of hydrogen production since the 1960s, when high pressureoperation was introduced.

Two potential problems arising from the reforming reactions includemetal dusting and coking, which can lead to process inefficiencies andequipment failure. Metal dusting occurs when the combination oftemperature, pressure and composition within a carbonaceous gaseousenvironment leads to corrosive degradation of alloys into dust. Metaldusting conditions can be difficult to avoid in reformer systems andthus metal dusting is a constant threat. Coking occurs when the gaseoushydrocarbons crack to produce a solid carbonaceous material which mayclog or damage flow paths, which can lead to heat transfer andconversion inefficiencies and equipment failure.

Industrial steam reformers are conventionally of tubular construction,employing several large metal tubes packed with the reforming catalyst.The hydrocarbon/steam feed mixture flows through the tubes, contactingthe catalyst and undergoing conversion to syngas. Because the reformingreactions are endothermic, heat must be supplied to maintain therequired reforming temperatures (generally above 800° C.). Inconventional tubular reforming systems, this is accomplished by placingthe tubes in a combustion furnace, usually fired by natural gas, wherethe heat is transmitted to the tubes by a combination of convective andradiant heat transfer.

Thus, the successful operation of a tubular reformer relies onmaintaining a somewhat delicate balance between the endothermicreforming reactions within the tubes and the heat transfer to the tubesfrom the furnace combustion. The heat flux through the tube walls mustbe sufficiently high to maintain the required temperatures for thereforming reactions, but must not be so high as to give rise toexcessive metal wall temperatures (accompanied by strength reduction) orto coking of the hydrocarbon at hot spots within the tubes. Therefore,the operation of tubular reformers must be subject to stringent control.

While large-scale tubular reformers have been very successful bothtechnically and economically, small-scale tubular reformers are lesssuccessful. Amongst other things, the costs to manufacture, install,maintain and operate tubular reformers on a smaller scale areunattractive.

Smaller users of syngas downstream products such as hydrogen, ammoniaand methanol have therefore not found it attractive to establish on-siteproduction facilities for those products. Rather, they generally rely ontruck-delivery of cylinders of the product from bulk producers. Thissolution is becoming less attractive as the price of transport fuelsincreases. Also, many such users with access to natural gas would preferto have on-site production facilities not only to avoid transport costsbut also to enhance the reliability of their supply. Additionally, muchof the world's natural gas supply lies in small fields in remote regionsnot served by pipelines to the natural gas market. The energy content ofthis so-called “stranded gas” could be more easily transported to marketif the gas were first converted to liquids such as methanol andlong-chain hydrocarbons, which may be produced from syngas.

Therefore there is a need for the production of syngas on a smallerscale than has been economically and practically feasible withconventional tubular systems, and that need is likely to increase. Thereare considerable challenges, however: a smaller-scale system must bereasonably proportionate to large scale plant in initial cost, andoperating costs must also be proportionate to the scale of production.Low operating costs require high energy efficiency, minimizing naturalgas costs, simplicity of operation and minimizing or avoiding the needfor attention from full-time plant operators.

While the amount of heat required by the reforming reactions is fixed bythermodynamics, the overall efficiency of energy usage in the plant isdependent upon the effectiveness with which heat is recovered from thehot syngas and hot combustion flue streams to preheat the cold feeds toreforming temperatures and raise the necessary steam. High-effectivenessfeed-effluent heat exchangers and the use of flue-heated pre-reformerscan assist in this regard. Importantly, whilst large-scale reformingsystems might claim energy efficiency credit for the energy content ofexcess steam exported to other processes on the site, small-scalereforming systems are unlikely to have an export destination availablefor excess steam and hence its production does not enhance efficiency.

Both initial capital costs and operational simplicity may be enhanced byminimizing the use of active control, using instead passive controltechniques where possible. For example, the suitable splitting of asingle stream to pass to several components connected in parallel can beachieved by arranging for suitable relative pressure drops through thosecomponents, without the use of control valves. As a further example, thetemperature of a stream exiting a heat exchanger can be held withinclose limits by arranging for the heat exchanger to operate with a smalltemperature pinch.

An additional consideration in small-scale systems is that the usermight not operate continuously at or near full plant capacity, incontrast to large-scale plants. Therefore modulation of throughputthrough a wide range should be achievable and subject to automation, asshould fast start-up and shut-down procedures.

The small-scale reformer should also minimize maintenance requirements.

Thus, there is a need for a small-scale reforming process and apparatuswhich will accomplish the goal of being capital and operatingcost-competitive with large-scale systems as a result of simplicity ofcontrol, monitoring and maintenance together with high energyefficiency.

BRIEF SUMMARY OF THE INVENTION

In some embodiments, a gaseous hydrocarbon-steam reforming processand/or apparatus may be designed to limit the occurrence of metaldusting conditions to localized portions of the apparatus or process. Insome embodiments, the localized portions of the apparatus or process towhich the occurrence of metal dusting conditions are limited may includea fuel pre-heater wherein a fuel/air mixture is partially combusted toheat a fuel stream from below the metal dusting temperature to above themetal dusting temperature. In some embodiments, the localized portionsof the apparatus or process to which the occurrence of metal dustingconditions are limited may include an air pre-heater wherein a fuel/airmixture is combusted to heat an air stream from below the metal dustingtemperature to above the metal dusting temperature. In some embodiments,the localized portions of the apparatus or process to which theoccurrence of metal dusting conditions are limited may include a portionof the piping adjacent to a quench heat exchanger where a portion of thesyngas stream formed during the reformer process is quenched from abovethe metal dusting temperature to below the metal dusting temperature. Insome embodiments, the localized portions of the apparatus or process towhich the occurrence of metal dusting conditions are limited may includea portion of the process piping where the quenched syngas is mixed witha second portion of the syngas that has not been quenched.

Accordingly, in some embodiments, the gaseous hydrocarbon-steamreforming process may include

a) preheating one or more air streams to form one or more preheated airstreams;

b) combining at least one air stream with a portion of at least one fuelstream to form a fuel/air mixture having a temperature below metaldusting conditions;

c) partially combusting the fuel in a portion of the fuel/air mixture toform a heated fuel stream having a temperature above metal dustingconditions for use in one or more reformer stages;

d) combusting a portion of the fuel/air mixture in the presence of atleast one of the preheated air streams to form a heated air streamhaving a temperature above metal dusting conditions for use in reformingfor use in one or more reformer stages;

e) heating one or more water streams to form steam;

f) mixing the steam with one or more gaseous hydrocarbon streams to forma gaseous hydrocarbon-steam stream;

g) heating and partially reforming the gaseous hydrocarbon-steam streamin one or more pre-reforming stages to form a reformer stream, whereinthroughout the one or more pre-reforming stages the gaseoushydrocarbon-steam stream has a combination of temperature andcomposition that avoids metal dusting and coking conditions;

h) reforming the reformer stream in one or more reformer stages to forma syngas stream and a flue gas stream, wherein throughout the one ormore reforming stages the reformer stream has a combination oftemperature and composition that avoids metal dusting and cokingconditions;

i) recovering heat from the flue gas stream to provide heat to thepre-reforming stages in step g) and to provide preheating to the waterstream; and

j) recovering heat from the syngas stream to preheat the air stream fromstep a) and to provide heat to form steam in step e).

In some embodiments, the process or apparatus comprises a process orapparatus for steam reforming of gaseous hydrocarbons to produce syngaswhere the feed rate of the gaseous hydrocarbon is from 1 to 10,000standard cubic meters per hour (“SCMH”). In some embodiments, theprocess or apparatus is configured to minimize, avoid or localize theoccurrence of metal dusting and/or coking conditions throughout thesteam reforming process. Preferably, the process or apparatus isconfigured to avoid metal dusting conditions in the heat exchangers,reforming stages and pre-reforming stages of the process or apparatus.Preferably, the process or apparatus is configured to avoid cokingconditions in the fuel feed streams, in the pre-reforming and reformingstages and/or in the syngas streams.

In some embodiments, the process or apparatus comprises a process orapparatus for steam reforming of gaseous hydrocarbons to produce syngas,where the process has a hydrocarbon conversion of greater than 50% andless than 95%. In some embodiments, the process or apparatus comprises aprocess or apparatus for steam reforming of gaseous hydrocarbons toproduce syngas, where the process has an energy efficiency of greaterthan 50%. In some embodiments, the process or apparatus comprises aprocess or apparatus for steam reforming of gaseous hydrocarbons,wherein all steam required for the process is generated and used withinthe process, i.e. there is no steam export from or import into theprocess.

In some embodiments, a process or apparatus for steam reforming ofgaseous hydrocarbons comprises a passive flow control system whereby theappropriate amount of fuel and air are delivered to various points inthe process, such as the pre-heaters, the pre-reforming stages and/orthe reforming stages by means of pressure drop balancing within the heatexchangers, the pre-reformer stages and/or the reformer stages.

In general, steam reforming of gaseous hydrocarbon streams is believedto involve the following reactions:

C_(n)H_(m) +nH₂

nCO+(n+m/2)H₂  (1);

and

CO+H₂O

CO₂+H₂  (2)

Equation (1) reduces to

CH₄+H₂O

CO+3H₂  (3)

when the gaseous hydrocarbon is methane.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1A shows a schematic of an embodiment of a reforming system.

FIG. 1B shows a schematic of an alternative configuration for a portionof the reforming system according to FIG. 1A, FIG. 5 and FIG. 7.

FIG. 2A-C show schematics of plates that may be used to form anembodiment of syngas heat recovery heat exchanger 110 as identified inFIG. 1A.

FIG. 3A-B show schematics of plates that may be used to form anembodiment of heat exchanger 164 as identified in FIG. 1A, FIG. 5 andFIG. 7.

FIG. 4A-D show schematics of plates that may be used to form anembodiment of heat exchanger 166 as identified in FIG. 1A, FIG. 5 andFIG. 7.

FIG. 5 shows a schematic of an alternate embodiment of a reformingsystem.

FIG. 6A-C show schematics of plates that may be used to form anembodiment of syngas heat recovery heat exchanger 510 as identified inFIG. 5.

FIG. 7 shows a schematic of an alternate embodiment of a reformingsystem.

FIG. 8 shows a schematic for an embodiment of reformer module 150 asidentified in FIG. 1A, FIG. 5 and FIG. 7 including a reformer andpre-reformer.

FIG. 9A-E show schematics of plates that may be used to form anembodiment of a pre-reformer.

FIG. 10A-B show schematics of plates that may be used to form a cell ina pre-reformer.

FIG. 11A-F show schematics of plates that may be used to form anembodiment of a reformer.

FIG. 12A-D show schematics of plates that may be used to form a cell ina reformer.

FIG. 13A-B show a bottom view of a stack plates forming a pre-reformer(FIG. 13A) and reformer (FIG. 13B).

FIG. 14 shows an illustration of the desired trends of the temperatureprofiles for the reformer air stream and the reformer stream in anembodiment.

FIG. 15 shows an embodiment of a flow resistance network for the air andfuel streams in a reforming system.

FIG. 16A-D show schematics of plates that may be used to form anembodiment of a reformer.

FIG. 17 shows a simulated syngas temperature distribution for a reformercross-flow heat exchanger without taking wall conduction into account.

FIG. 18 shows a simulated syngas temperature distribution for a reformercross-flow heat exchanger taking wall conduction into account.

FIG. 19 shows a graph of the composite hot and cold temperature-enthalpycurves for the process streams in an embodiment of a reformer system.

FIG. 20 shows a front perspective view of a partial configuration for anembodiment of a reformer system 100.

FIG. 21 shows a rear perspective view of a partial configuration for anembodiment of a reformer system 100 shown in FIG. 20.

DEFINITIONS

Metal dusting conditions: the combination of temperature and compositionwithin a carbonaceous gaseous environment that leads to corrosivedegradation of structural materials and alloys into dust. In general,metal dusting occurs at intermediate temperatures between 400° C. and800° C. and where the activity of the carbon in the gas phase (“a_(C)”)is greater than 1. Because metal dusting is a result of a combination oftemperature and composition in a given stream, either of these variablesmay be manipulated to avoid or reduce the occurrence of metal dustingconditions. Accordingly, for some compositions, the upper limit formetal dusting may be less than 800° C. such as 700° C. or 750° C. andthe lower limit may be higher than 400° C. such as 420° C. or 450° C.Thus, it should be understood that 400° C. to 800° C. is intended as ageneral rule of thumb, but that there are exceptions and that metaldusting conditions involve the combination of composition andtemperature. Accordingly, when this application mentions “metal dustingconditions are avoided or reduced” and the like, it is intended that thecombination of the variables that may lead to metal dusting conditionsare avoided or reduced by either manipulating temperature, compositionor both.

While not wishing to be bound by any theories, metal dusting is believedto be, for the most part, a result of the following reactions:

CO+H₂

C+H₂O  (4)

and

2CO

CO₂+C  (5)

Accordingly, metal dusting conditions may be avoided or reduced bymanipulating the temperature and/or composition of a gaseous stream toavoid these reaction situations and to avoid conditions where a_(C)>1.Alternatively, the process and/or apparatus may be designed to limit theoccurrence of metal dusting conditions to localized points of theprocess and/or apparatus to minimize repair requirements, minimizedifficulty and cost of repair and minimize requirements for use ofcostly alloys or coated materials that are resistant to metal dusting.

Metal dusting resistant materials: Metal dusting resistant materials arematerials that resist corrosive degradation when exposed to metaldusting conditions. Any materials that are metal dusting resistant andotherwise are suitable for the relevant process conditions such astemperature and pressure may be used. In some embodiments, the metaldusting resistant materials may be Alloy 617, Alloy 617 coated with analuminide coating or Alloy 800H coated with an aluminide coating. Thealuminide coating may be formed by depositing aluminium onto the surfaceof the material, diffusing it into the alloy at high temperature andoxidizing it.

Catalysts: In general, when the term catalyst is used herein withrespect to the reforming or combustion beds or chambers, it is intendedto include any suitable catalyst, such as any suitable non-precious orprecious metal catalyst or mixtures and combinations thereof, which maybe a structured or unstructured catalyst and may be a supported orunsupported catalyst. Suitable unstructured catalysts may include porousparticulate catalysts which may have their size optimized to achieve thedesired reforming reaction or combustion, while maintaining the desiredpressure drop within the relevant stream. Suitable structured catalystsmay be coated on a metallic wire mesh or metal foil support or on aceramic matrix. In some embodiments, the catalyst may comprise a metalcatalyst comprising a metal selected from: gold, silver, platinum,palladium, ruthenium, rhodium, osmium, iridium, or rhenium orcombinations of one or more thereof. In some embodiments, the catalystmay be a platinum/palladium catalyst on an alumina washcoat supportcoated on a fecralloy (iron-chromium-aluminium) metal foil matrix.

Alternatively, when using the term catalyst when referring to awater-gas shift reactor catalyst, it is intended to include any suitablecatalyst, such as a non-precious or precious metal catalyst or mixturesand combinations thereof, which may be a structured or unstructuredcatalyst and may be a supported or unsupported catalyst. Suitableunstructured catalysts may include porous particulate catalysts whichmay have their size optimized to achieve the desired water-gas shiftreaction, while maintaining the desired pressure drop within therelevant stream. Suitable structured catalysts may be coated on ametallic wire mesh or metal foil support or on a ceramic matrix.

DETAILED DESCRIPTION

In some embodiments, the process or apparatus comprises a process orapparatus for steam reforming of gaseous hydrocarbons to produce syngaswhere the feed rate of the gaseous hydrocarbon is from 1 to 10,000standard cubic meters per hour (“SCMH”), such as from 2 to 5000 SCMH,such as 1 to 10, 10 to 100, 100 to 1000, 1000 to 10,000, 10 to 4000, 15to 3000, 20 to 2000, 30 to 1000, 40 to 500, 50 to 250 or 60 to 100 SCMH.

In some embodiments, a process or apparatus for steam reforming ofgaseous hydrocarbons to produce syngas, may have a hydrocarbonconversion of 50% or greater such as from 50% to 95%, such as from 55%to 90%, from 60% to 85%, from 65% to 80% or from 70% to 75%.

In some embodiments, a process or apparatus for steam reforming ofgaseous hydrocarbons to produce syngas, may have an energy efficiency offrom 50% to 90%, such as from 55% to 85%, from 60% to 80% or from 65% to75% when calculated according to the following equation:

$\frac{\left( {{{LHV}_{s}*M_{s}} - {{LHV}_{f}*M_{f}}} \right)}{{LHV}_{ng}*M_{ng}}$

-   -   where    -   LHV_(S)=the amount of heat released per mole (or per kg) by        combustion of the syngas product, excluding water latent heat;    -   M_(s)=the molar (or mass) flow rate of the syngas product;    -   LHV_(f)=the amount of heat released per mole (or per kg) by        combustion of the fuel, excluding water latent heat;    -   M_(f)=the molar (or mass) flow rate of the fuel;    -   LHV_(ng)=the amount of heat released per mole (or per kg) by        combustion of the natural gas, excluding water latent heat; and    -   M_(ng)=the molar (or mass) flow rate of the natural gas.

In some embodiments, the process or apparatus comprises a process orapparatus for steam reforming of gaseous hydrocarbons having theefficiencies described above and wherein all steam required for theprocess is generated and used within the process, i.e. there is no steamexport from, or import into, the process.

In some embodiments, the process or apparatus is configured to minimize,avoid or localize the occurrence of metal dusting and/or cokingconditions throughout. Preferably, the process or apparatus isconfigured to avoid metal dusting conditions in the heat exchangers, thepre-reforming stages and/or the reforming stages of the process orapparatus. Preferably, the process or apparatus is configured to avoidcoking conditions in the gaseous hydrocarbon feed streams, the fuel feedstreams, in the pre-reforming and reforming stages and/or in the syngasstreams. In some embodiments, the process and/or apparatus may bedesigned to limit the occurrence of metal dusting conditions tolocalized points or components of the process and/or apparatus, such asto localized points of the process or apparatus that may be designed orconstructed from metal dusting resistant or protected materials and/orconfigured for easy and/or lower cost repair and/or replacement.

In some embodiments, the process or apparatus for steam reforming ofgaseous hydrocarbons comprises a passive flow control system whereby theappropriate amount of fuel and air are delivered to various points inthe process, such as the pre-heater and the combustion stages of thereforming system by means of pressure drop balancing within the heatexchangers, the pre-reformer stages and/or the reformer stages.

In some embodiments, the gaseous hydrocarbon-steam reforming processcomprises:

partially combusting the fuel in a first fuel/air mixture stream to heatthe first fuel/air mixture stream for use during reforming of thegaseous hydrocarbon-steam stream;

combusting a second fuel/air mixture stream to heat an air stream foruse during reforming of the gaseous hydrocarbon-steam stream; and

reforming the gaseous hydrocarbon-steam to form a syngas stream and aflue gas stream.

Partially combusting may comprise catalytically oxidizing at least aportion of the fuel in the first fuel/air mixture stream to provide aheated fuel stream. The partial combustion may use all or substantiallyall of the air in the first fuel/air mixture stream. After the partialcombustion, the heated fuel stream may be provided to one or morereformer stages for further combustion to heat or re-heat one or moreair streams. Combusting a second fuel/air mixture stream may comprisecatalytically oxidizing all or substantially all of the fuel in thesecond fuel/air mixture stream to provide a heated air stream. Theheated air stream may be provided to one or more reformer stages toprovide heat to the gaseous hydrocarbon-steam stream being reformed. Theresulting cooled air stream may then be heated or re-heated, for exampleby combustion of a portion of the heated fuel stream in the presence ofthe cooled air stream.

In some embodiments, reforming includes pre-reforming the gaseoushydrocarbon-steam stream to form a reformer stream, prior to reformingthe reformer stream. In some embodiments, reforming includes reducingmetal dusting and/or coking during reforming by heating andpre-reforming the gaseous hydrocarbon-steam stream in multiplepre-reforming stages to form a reformer stream, prior to reforming thereformer stream. In some embodiments, the pre-reforming includespartially reforming a portion of the gaseous hydrocarbon-steam stream.In some embodiments, partially reforming includes multiple pre-reformingstages, each stage including a) heating the gaseous hydrocarbon-steamstream followed by b) partial catalytic reforming of the gaseoushydrocarbon-steam stream. The heating may include recovering heat from aflue gas stream of the reforming process. The number of pre-reformingstages may be from 1 to 10 such as from 2 to 7 or 3 to 5 pre-reformingstages. In some embodiments, pre-reforming is performed in multiplestages to help avoid or reduce coking conditions during pre-reformingand reforming. In some embodiments, coking conditions are avoided orreduced during pre-reforming by altering the composition and/ortemperature of the gaseous hydrocarbon-steam stream. In someembodiments, pre-reforming is conducted in a printed circuit reactor(“PCR”).

The reformer stream may be reformed in one or more stages of catalyticreforming. In some embodiments, the reforming is conducted in a PCR. Insome embodiments, the reforming comprises from 1 to 40 stages ofreforming, such as from 2 to 35 stages, from 3 to 30 stages, from 5 to25 stages, from 8 to 20 stages or from 10 to 15 stages of catalyticreforming. In some embodiments, reforming the gaseous hydrocarbon steamstream includes at least three stages of:

i) heating the reformer stream by recovering heat from a heated airstream in a heat exchanger to form a heated reformer stream and a cooledair stream;

ii) reforming at least a portion of the heated reformer stream; and

iii) combusting a portion of a partially combusted fuel/air mixturestream in the presence of the cooled air stream to re-heat the cooledair stream.

In some embodiments, heating the reformer stream includes recoveringheat in a heat exchanger from a heated air stream, such as the heatedair stream made by combusting the second fuel/air mixture stream, or theheated air stream made by combusting a portion of the partiallycombusted fuel/air mixture stream in the presence of a cooled air streamto re-heat the cooled air stream. In some embodiments, the heatexchanger may comprise a co-flow, a cross-flow or a counter-flow heatexchanger. Preferably, the heat exchanger comprises a cross-flow heatexchanger. In some embodiments, the heat exchanger comprises a printedcircuit heat exchanger. Preferably, the pressure drop across the heatexchanger for the heated air stream is less than 0.1 bar, such as lessthan 0.09 bar, less than 0.07 bar, less than 0.06 bar or less than 0.05bar. In some embodiments, the pressure drop across the heat exchangerfor the reformer stream is less than 0.5 bar, such as for example, lessthan 0.4 bar, less than 0.30 bar, less than 0.2 bar or less than 0.1bar.

Reforming at least a portion of the heated reformer stream may includecatalytically reforming a portion of the heated reformer stream toproduce syngas. The reforming may be conducted through a series ofcatalytic reformation stages to maximize hydrocarbon conversion, whilereducing or avoiding coking conditions in the reformer stream in thereformer. Preferably, the conversion of the gaseous hydrocarbon occursaccording to Equation (1). In addition, additional production ofhydrogen may occur via the water-gas shift reaction as follows:

CO+H₂O→CO₂+H₂  (6).

which may approach equilibrium during reforming and pre-reforming.

In some embodiments, combusting a portion of the partially combustedfuel/air mixture stream in the presence of the cooled air stream tore-heat the cooled air stream includes catalytic combustion of a portionof the partially combusted fuel/air mixture stream in the presence ofthe cooled air stream. In some embodiments, the portion of the partiallycombusted fuel/air mixture stream is supplied separately to thecatalytic combustion chambers of a portion of, or all of, the reformerstages. In some embodiments, the portion of the partially combustedfuel/air mixture stream supplied to the reformer stages is the sameamount of the partially combusted fuel/air mixture stream for eachreformer stage supplied.

In other embodiments, the portion of the partially combusted fuel/airmixture stream supplied to the reformer stages varies depending on thestage supplied. In some embodiments, the amount of the partiallycombusted fuel/air mixture supplied to one or more of the combustingsteps of the second and subsequent stages of the reformer may be lessthan that supplied to one or more of the preceding stages. For example,in some embodiments, the amount of the partially combusted fuel/airmixture stream supplied may reduce successively for each stage ofreforming and in some embodiments, one or more later stages of reformingmay have no portion of the partially combusted fuel/air mixture streamsupplied to it. Preferably, the amount of the partially combustedfuel/air mixture supplied to the reformer stages reduces for eachsuccessive stage and may be zero for one or more stages.

The portion of the partially combusted fuel/air mixture stream suppliedto each stage of reforming may be controlled using active or passivecontrols. Preferably the portion of the partially combusted fuel/airmixture stream supplied to each stage of reforming is controlled usingpassive flow control. Such passive flow control may be accomplished bybalancing pressure drops in the fuel streams, the air streams, thefuel/air mixture streams and/or its component streams throughout thereformer and heat exchange components of the reforming process.

After the last reforming stage has been completed, two streams leave thereformer from which heat may be recovered. The first stream is thesyngas stream, which is the reformed gaseous hydrocarbon-steam stream.The second stream is the flue gas stream, which is the air streamleaving the last heat exchanger from the last reformer stage. Each ofthese streams is at relatively high temperatures.

In some embodiments, the process or apparatus achieves the efficienciesdescribed herein in part by recovering heat from the flue gas and/or thesyngas streams leaving the reformer stages. In some embodiments, heat isrecovered from the syngas stream into one or more reactant feed streams,such as one or more of: a gaseous hydrocarbon stream, one or more fuelstreams, one or more air streams and one or more water streams in one ormore heat exchangers. In some embodiments, heat is recovered in one ormore heat exchangers from the flue gas stream to heat the gaseoushydrocarbon-steam stream in one or more of the pre-reformer stages. Insome embodiments, heat is recovered from the flue gas stream by both thegaseous hydrocarbon steam-stream and one or more water streams. In someembodiments where heat is recovered from the flue gas stream by both thegaseous hydrocarbon steam-stream and one or more water streams, the fluegas stream is heated prior to exchanging heat with the water stream bycombusting a portion of at least one fuel stream in the presence of theflue gas stream. In some embodiments, the water stream recovers heatfrom both the flue gas stream and the syngas stream. In someembodiments, heat is recovered from at least a portion of the syngasstream by quenching at least a portion of the syngas stream in a quenchheat exchanger.

In some embodiments, the gaseous hydrocarbon-steam reforming processcomprises:

a) preheating one or more air streams to form one or more preheated airstreams;

b) combining at least one air stream with a portion of at least one fuelstream to form a fuel/air mixture having a temperature below metaldusting conditions;

c) partially combusting the fuel in a portion of the fuel/air mixture toform a heated fuel stream having a temperature above metal dustingconditions for use in one or more reformer stages;

d) combusting a portion of the fuel/air mixture in the presence of atleast one of the preheated air streams to form a heated air streamhaving a temperature above metal dusting conditions for use in one ormore reformer stages;

e) heating one or more water streams to form steam;

f) mixing the steam with one or more gaseous hydrocarbon streams to forma gaseous hydrocarbon-steam stream;

g) heating and partially reforming the gaseous hydrocarbon-steam streamin one or more pre-reforming stages to form a reformer stream, whereinthroughout the one or more pre-reforming stages the gaseoushydrocarbon-steam stream has a combination of temperature andcomposition that avoids metal dusting and coking conditions;

h) reforming the reformer stream in one or more reformer stages to forma syngas stream and a flue gas stream, wherein throughout the one ormore reforming stages the reformer stream has a combination oftemperature and composition that avoids metal dusting and cokingconditions;

i) recovering heat from the flue gas stream to provide heat to thepre-reforming stages in step g) and to provide preheating to the waterstream; and

j) recovering heat from the syngas stream to preheat the air stream fromstep a) and to provide heat to form steam in step e).

In some embodiments, the air stream is preheated by recovering heat fromthe syngas stream in a heat exchanger. In this way, at least a portionof the heat remaining in the syngas stream may be recovered, therebyimproving the efficiency of the process. The air stream may be anysuitable air stream, such as a process air stream or a blown air streamand may be conditioned or unconditioned, such as filtered or unfiltered,purified or unpurified or humidified or dehumidified. Preferably the airstream may be a forced air stream provided from a blower or other blownair source. Generally, it is preferred that the air is supplied at asufficient pressure for the process requirements, while not at anexcessive pressure that may cause inefficiency in the process due toincreased blower energy requirements. Accordingly, the process andapparatus is desirably configured to minimize the air pressure requiredin the process, which may be accomplished by avoiding large pressuredrops across process components, such as heat exchangers, valves, andpre-reforming and reforming stages.

In some embodiments combining at least one air stream with a portion ofat least one fuel stream to form a fuel/air mixture having a temperaturebelow metal dusting conditions includes joining an air stream and a fuelstream. In some embodiments, the at least one air stream is a portion ofthe air stream discussed above either before or after that air stream ispreheated. In some embodiments, the at least one air stream is a portionof the air stream discussed above prior to pre-heating. In this manner,there may be a single air stream provided to the system or process thatmay be split into two or more air streams prior to or after preheating.One or more of the air streams may be preheated in the same or differentheat exchangers by recovering heat from the syngas stream.

In some embodiments, the fuel stream may be preheated by recovering heatfrom the syngas stream, such as in a heat exchanger. In someembodiments, a portion of the fuel stream that is combined with the atleast one air stream is preheated in the same heat exchanger in whichone or more of the air streams described above is preheated. The fuelstream may be a portion of any suitable combustion fuel feed stream forsteam reforming processes, such as off-gas or tail gas streams from apressure swing adsorption process (PSA), from a methanol productionprocess or from an ammonia production process, or it may be a mixture ofan off-gas or tail gas with a gaseous hydrocarbon stream or streams suchas natural gas streams, methane streams, propane streams, mixtures ofgaseous hydrocarbons, refinery or other off gases or tail gases andmixtures or combinations thereof. The conditions during preheating arepreferably maintained to reduce or avoid metal dusting and cokingconditions in the fuel stream and in the heat exchanger.

The at least one air stream and the portion of the fuel stream may bejoined in any suitable manner, such as by joining the streams to form asingle stream using a “Y” or “T” connector or by adding one stream intothe other stream. In some embodiments, the at least one air stream andthe portion of the fuel stream may be joined in the heat exchanger bycombining the heat exchange streams of the two or by feeding the streamsto the same heat exchanger outlet. Preferably, the resulting fuel/airmixture is fuel rich and capable only of incomplete combustion due tothe limited amount of air in the stream.

In some embodiments, after the fuel/air mixture has been formed, it maybe split into two or more streams using any suitable splittingmechanism, such as a “Y” or “T” connection. At least one portion of thesplit fuel/air mixture may be partially combusted, such as catalyticallycombusted, to form a heated fuel stream, which may have a temperatureabove metal dusting conditions. Preferably, the combustion is partial asa result of the limited air in the mixture. In some embodiments, theheated fuel stream may contain substantially no combustible air and mayinclude fuel and combustion byproducts. In some embodiments, during thecombustion of the fuel/air mixture, the stream experiences metal dustingand/or coking conditions. In such cases, the components of the streamassociated with the combustion, including the combustion chamber, arepreferably constructed from metal dusting resistant materials, such asmetal dusting resistant alloys or alloys that have been coated withmetal dusting resistant coatings and/or are configured for easy repairand/or removal and replacement. Preferably, the temperature andcomposition of the heated fuel stream, after the combustion, areappropriate for use in the reformer stages with no further modificationand are such that the heated fuel stream will not experience metaldusting or coking conditions within the reformer stages.

A second portion of the fuel/air mixture may be combusted, such ascatalytically combusted in the presence of a preheated air stream toform a heated air stream for the reformer stages. In some embodiments,the heated air stream may have a temperature above metal dustingconditions. Preferably, the fuel in the fuel/air mixture is completelyor substantially completely combusted to provide additional heat to thepreheated air stream.

In some embodiments, heating one or more water streams to form steamincludes recovering heat from a flue gas stream and/or a syngas stream.In some embodiments, recovering heat from a syngas stream includesrecovering heat from a syngas stream at two different points in thegaseous hydrocarbon-steam reforming process, such as shortly after thesyngas stream leaves the reformer stages and just prior to the syngasstream leaving the process.

In some embodiments, the one or more water streams recovers heat fromthe flue gas stream in a heat exchanger after the flue gas stream hasleft the reforming and pre-reforming stages, such as just prior to theflue gas stream leaving the reforming process. In some embodiments, theflue gas stream may be combined with a portion of the fuel stream and/orthe gaseous hydrocarbon stream and then preheated by combusting, such ascatalytically combusting, the portion of the fuel stream and/or thegaseous hydrocarbon stream in the presence of the flue gas stream priorto entering the heat exchanger but after the flue gas stream has leftthe reforming and pre-reforming stages. In other embodiments, such asembodiments where the reforming is conducted as a high temperaturereforming process, this combustion step may not be included or used.

In some embodiments, the water stream recovers heat from a portion ofthe syngas stream shortly after the syngas stream leaves the reformerstages, the recovery occurring in a quench heat exchanger in which theentering syngas stream raises steam by exchanging heat with a waterstream in a heat exchanger that is submerged in the water. In suchembodiments, because the heat exchanger is submerged in water, metaldusting conditions are avoided as a result of the relatively constantmetal temperature due to boiling of the water, in conjunction withinsufficient pressure to raise the boiling point of the water to metaldusting temperatures. Though the heat exchanger does not experiencemetal dusting conditions, the syngas stream, shortly before entering thequench heat exchanger, may. Accordingly, that portion of the syngaspiping within at least five pipe diameters of the entrance to the heatexchanger is preferably constructed from metal dusting resistantmaterials, such as metal dusting resistant alloys or alloys that havebeen coated with metal dusting resistant coatings and/or is configuredfor easy repair and/or removal and replacement. In some embodiments, allor a majority of the steam raised and used in the gaseoushydrocarbon-steam reforming process is raised in the quench heatexchanger. In some embodiments, the syngas stream is split to form afirst syngas stream and a second syngas stream and heat is recovered inthe quench heat exchanger from one of the first and the second syngasstreams.

In some embodiments, the water stream recovers heat from the syngasstream just prior to the syngas stream leaving the gaseoushydrocarbon-steam reforming process. In some embodiments, this heatrecovery occurs in the same heat exchanger as the heat recovery for theair and fuel streams as discussed above. In other embodiments, aseparate heat exchanger is used for the heat recovery into the waterstream from the syngas stream just prior to the syngas stream leavingthe gaseous hydrocarbon steam reforming process.

In some embodiments, after the one or more water streams have beenheated to produce steam, the steam is mixed with one or more gaseoushydrocarbon streams to form a gaseous hydrocarbon-steam stream. Themixing may be accomplished by joining a steam stream with a gaseoushydrocarbon stream to form a single stream using any suitable means suchas using a “Y” or “T” connector or by adding one stream into the otherstream. In some embodiments, the gaseous hydrocarbon stream has beenpreheated, such as preheated by recovering heat from the syngas stream,such as in the same or a different heat exchanger as the heat recoveryfor the air and fuel streams as discussed above. The gaseous hydrocarbonstream may be any suitable gaseous hydrocarbon stream for steamreforming, such as natural gas, methane, propane, mixtures of gaseoushydrocarbons, refinery or other flue gases and mixtures or combinationsthereof. In some embodiments the ratio of steam to gaseous hydrocarbonin the gaseous hydrocarbon-steam stream may be indicated by a ratio ofsteam to carbon. In some embodiments the ratio of steam to carbon in thereformer stream may be from 1:1 to 12:1, such as from 2:1 to 10:1, from3:1 to 8:1 or from 4:1 to 6:1.

In some embodiments, the gaseous hydrocarbon-steam stream ispre-reformed in one or more pre-reforming stages. In some embodiments,the one or more pre-reforming stages include heating and partiallyreforming the gaseous hydrocarbon-steam stream to form a reformingstream. In such embodiments, the partial reforming may comprise one ormore stages of heating the gaseous hydrocarbon-steam stream byrecovering heat from the flue gas stream followed by partial catalyticreformation of the gaseous hydrocarbon-steam stream. In someembodiments, at least 2 stages of pre-reforming are performed, such asfrom 2 to 10, from 3 to 10, from 4 to 8 or from 5 to 7 pre-reformingstages such as 2 or more, 3 or more, 4 or more or 5 or morepre-reforming stages. In some embodiments, coking conditions are avoidedin the pre-reforming stages by modifying the temperature of the gaseoushydrocarbon-steam stream and/or by modifying the composition of thegaseous hydrocarbon-steam stream by heating and partially reforming itto avoid such conditions. In addition, in some embodiments, thepre-reforming stages provide a reformer stream to the first stage ofreforming that avoids metal dusting and coking conditions.

Reforming of the reformer stream in one or more reformer stages to forma syngas stream and a flue gas stream may be accomplished as describedelsewhere herein including the control of the heated fuel streamsupplied to the individual stages. For example, in some embodiments, thereforming may be accomplished in one or more reformer stages, each stagecomprising: i) heating the reformer stream by recovering heat from aheated air stream to form a heated reformer stream and a cooled airstream, ii) reforming at least a portion of the heated reformer stream;and iii) combusting a portion of a heated fuel stream in the presence ofthe cooled air stream to form the heated air stream for the next stage.Preferably, the reformer stream has a combination of temperature andcomposition that avoids coking and metal dusting conditions throughoutthe reformer stages.

In some embodiments, an apparatus for steam reforming of a gaseoushydrocarbon comprises:

a) a fuel pre-heater that partially combusts the fuel in a firstfuel/air mixture to form a heated fuel stream, the heated fuel streambeing combusted in a reformer module;

b) an air pre-heater that combusts a second fuel/air stream in thepresence of an air stream to form a heated air stream, the heated airstream supplying heat to the reformer module; and

c) a reformer module for forming a syngas stream from a reformer stream.

The fuel and air pre-heaters may comprise any suitable catalyticcombustion chamber and may comprise a separate catalytic reactor or maycomprise a modified section of pipe that has been loaded with structuredor unstructured catalyst. In general, the catalytic combustion involvescatalytic oxidation of combustible components in the relevant stream toproduce heat as a result of the highly exothermic oxidation reaction.The combustion reaction may be catalyzed using any suitable catalystand/or may include or comprise non-catalytic combustion in conjunctionwith an ignition source or a flame source for start-up.

In some embodiments, the reformer module may comprise one or more, suchas 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8or more, 9 or more or 10 or more pre-reformer stages. In someembodiments, the reformer module may comprise from 2 to 10, 3 to 8 or 4to 7 pre-reformer stages. After the pre-reformer stages, the reformermodule may comprise from 1-40 reformer stages, such as from 2 to 35stages, from 3 to 30 stages, from 5 to 25 stages, from 8 to 20 stages orfrom 10 to 15 reformer stages. Each pre-reformer stage may comprise atleast one heat exchanger and at least one pre-reforming bed. Anysuitable heat exchanger and catalytic pre-reforming bed may be used.

In some embodiments, the one or more pre-reformer stages may comprise aPCR. The PCR may be configured similar to a printed circuit heatexchanger (“PCHE”) as known in the art, with catalyst chambers or bedsintermittently placed within the flow path of the gaseoushydrocarbon-steam stream such that the stream may be alternately heatedin a heat exchanger or heat exchange portion and then partially reformedcatalytically in a catalyst chamber or bed in a series of pre-reformingstages. In this regard, the PCR may comprises a series of plates havingone or multiple channels for flow of the gaseous hydrocarbon-steamstream and the flue gas stream in proximity to each other to exchangeheat. The channels for the individual streams may be etched or otherwiseformed on separate plates, which may then be stacked and diffusionbonded or otherwise bonded into a heat exchanger configuration such thatthe channels are brought into close proximity with each other and heatis exchanged through the channel walls. The stacking may includestacking of end plates, bounding plates and specific configurations ofgaseous hydrocarbon-steam and flue gas plates according to the desiredheat transfer. The channels on each plate may be configured for singleor multiple pass heat transfer between the streams, and when formed intoa PCR may be configured to operate in co-flow, cross-flow orcounter-flow. In some embodiments, the plates for one of the streams maybe configured for multiple passes, while the plates for the other streamare configured for single passes.

Each of the gaseous hydrocarbon-steam and flue gas plates may includemultiple pre-reforming catalyst chamber or bed penetrations, such thatwhen the plates are stacked and bonded into a heat exchangerconfiguration, the plates form multiple heat exchange zones, where heatis exchanged from the flue gas channels into the gaseoushydrocarbon-steam stream channels, and multiple reforming zones, wherethe heated gaseous hydrocarbon-steam stream is partially catalyticallyreformed. The reforming zones may be formed by aligning thepre-reforming catalyst chamber or bed penetrations when the plates arestacked to form chambers in which catalyst may be placed either,supported or unsupported.

In this regard, in some embodiments the PCR may operate as follows: thegaseous hydrocarbon-steam stream may enter the gaseous hydrocarbon-steamstream plate channels of the PCR, where it may be heated by the hotstream, which may be the flue gas stream from the reformer stagesflowing in the channels of the flue gas plate. After heating, thegaseous hydrocarbon-steam stream plate channels may direct the gaseoushydrocarbon-steam stream to a pre-reforming chamber or bed containingcatalyst, in which the gaseous hydrocarbon-steam stream may be partiallycatalytically reformed. After being partially reformed, the gaseoushydrocarbon-steam stream may proceed into plate channels further alongthe plate, where the stream will be re-heated by flue gas flowing in theflue gas plate channels of the flue gas plate. In this manner, thepartial reforming may included multiple iterations of the heating andpartial reforming in a single structure comprising end plates, boundingplates one or more flue gas plates and gaseous hydrocarbon-steam plates.

After the pre-reformer stages, the reformer module may comprise from1-40 reformer stages, such as from 2 to 35 stages, from 3 to 30 stages,from 5 to 25 stages, from 8 to 20 stages or from 10 to 15 stages ofcatalytic reforming. The reformer module may be configured in anysuitable manner for converting the reformer stream leaving thepre-reformer stages into syngas. Such reforming may include one or moreheat exchangers that heat the reformer stream by recovering heat from ahot stream, such as a heated air stream. The hot stream may providesufficient heat to the reformer stream to promote reforming in one ormore catalytic reforming beds. The reforming beds may catalyticallyreform the reformer stream in an endothermic reaction, thereby coolingthe reformer stream. The reformer stream may then be re-heated byrecovering heat from a hot stream, such as a heated air stream and thenmay be directed to one or more additional reformer beds. In this manner,the steps may be repeated through the reformer stages.

In some embodiments, the reformer module may comprise multiple stages,where each stage includes i) a heat exchanger that heats the reformerstream by recovering heat from a heated air stream to form a cooled airstream; ii) a reforming bed that reforms the heated reformer stream; andiii) a combustion chamber that combusts a portion of a heated fuelstream to re-heat the cooled air stream.

In some embodiments, the apparatus may include a fuel distributioncontrol network that is configured to passively control the amount ofthe heated fuel stream that is supplied to each combustion chamber inthe reformer stages. This configuration may be obtained by designing theapparatus and the individual heat exchange and reformer components ofthe apparatus to balance the pressure drops in the air and the fuelstreams throughout the apparatus to supply the appropriate amount of airand fuel to each combustion chamber in the reformer stages. In someembodiments, the fuel distribution control network is configured tosupply an amount of the heated fuel stream to one or more of thecombustion chambers of the second and subsequent reformer stages that isless than the amount of the heated fuel stream supplied to one or moreof the preceding stages. In some embodiments, the fuel distributioncontrol network is configured to supply an amount of the heated fuelstream to each of the combustion chambers of the second and subsequentreformer stages that is less than the amount of the heated fuel streamsupplied to the preceding stage.

As with the pre-reforming stages, in some embodiments, the reformerstages may comprise a PCR. In some embodiments, the PCR making up thereformer stages may be comprised of end plates, bounding plates, airflow plates, fuel flow plates, and reformer stream plates. Each of theactive plates may include flow channels for the relevant feed stream(air, fuel or reformer), multiple catalytic combustion chamberpenetrations and multiple catalytic reforming bed penetrations. Whencombined into a stack and diffusion bonded or bonded otherwise, themultiple catalytic combustion chamber penetrations and multiplecatalytic reforming bed penetrations of each plate may be aligned withthe corresponding penetrations of the other plates in the stack to formmultiple catalytic combustion chambers and multiple catalytic reformingbeds.

In some embodiments, such a printed circuit reactor may operate asfollows. A heated air stream flows through the flow channels of the airflow plates and exchanges heat with the reformer stream flowing throughthe flow channels of the reformer plate to heat the reformer stream andcool the air stream. The reformer stream then enters the first catalyticreforming bed, where it is catalytically reformed in an endothermicreaction, cooling the reformer stream and converting a portion of thestream to syngas. The cooled air stream proceeds to the first catalyticcombustion chamber where it is joined by a portion of the heated fuelstream, which is catalytically combusted to re-heat the air stream. There-heated air stream then exchanges heat with the cooled reformer streamand the process may be repeated through multiple stages. In someembodiments, the portion of the heated fuel stream is supplied inparallel to each of the combustion chambers. In some embodiments, eachcombustion chamber is supplied with the same amount of fuel from theheated fuel stream. Preferably, the amount of the heated fuel streamsupplied to each of the combustion chambers after the first combustionchamber is reduced relative to the preceding combustion chamber.Preferably, the supply of the heated fuel stream is passivelycontrolled. Ultimately, the streams leaving the reformer module comprisea syngas stream formed from the reformer stream and a flue gas streamcomprising the air stream, any residual fuel components and the fuelcombustion components.

In some embodiments, the apparatus for steam reforming of a gaseoushydrocarbon may further include at least one heat exchanger thatrecovers heat from the syngas stream after it leaves the reformermodule. In some embodiments, the apparatus comprises at least two heatexchangers for recovering heat from a portion of the syngas stream. Insome embodiments, at least one of the at least one heat exchangers is aquench heat exchanger. The quench heat exchanger may comprise a heatexchanger that is submerged in water. A portion of the hot syngas mayenter the quench heat exchanger at a temperature at/or above metaldusting temperatures and may be quenched to a temperature below metaldusting conditions. Because the heat exchanger is submerged in water,the heat exchanger never sees metal dusting conditions because thetemperature of the water will remain essentially constant as it boilsand as a result of the high heat transfer coefficient of boiling waterthe metal of the submerged heat exchanger will remain essentially at theboiling temperature of the water. The steam produced by quenching thesyngas stream in this manner may be combined with the gaseoushydrocarbon stream prior to entering the reformer module. Though thequench exchanger avoids metal dusting conditions, a portion of thesyngas piping adjacent to the entrance to the quench exchanger mayexperience metal dusting conditions and thus this portion of theapparatus is preferably constructed from metal dusting resistantmaterials or from material coated with a metal dusting resistant coatingand/or is configured for easy repair and/or removal and replacement.

The submerged heat exchanger is preferably a PCHE that relies on athermosyphon effect to exchange the heat from the syngas stream into thewater, circulating water through the exchanger as a result of thedensity differences between the boiling water and the single phasewater. The PCHE may comprise one or more syngas plates and one or morewater plates which together may be the “active” plates within theexchanger. The syngas plates may have multiple flow channels etched orotherwise provided thereon through which the syngas flows. The waterplates may have multiple flow channels etched or otherwise providedthereon, through which the water/steam flows. The water and syngasplates, along with bounding plates and/or endplates may be stacked intoa heat exchanger configuration. In this configuration, the PCHE maycomprise a series of stacked and diffusion bonded or other wise bondedplates having multiple channels for flow of the syngas and water streamsin proximity to each other to exchange heat from the syngas streams tothe water streams. The PCHE may be formed by stacking end plates,bounding plates and specific configurations of syngas and water streamplates according to the desired heat transfer. The channels on eachplate may be configured for single or multiple pass heat transferbetween the streams, and when formed into a heat exchanger may beconfigured to operate in co-flow, cross-flow or counter-flow.Preferably, the heat exchanger formed from the plates is configured inco-flow to avoid dryout in the passages on the water side of theexchanger. In some embodiments, the plates for one of the streams may beconfigured for multiple passes, while the plates for the other areconfigured for single passes.

The water level in the quench exchanger may be controlled using anysuitable method such as known water level control means for controllingboiler water levels. The submerged heat exchanger may be partially orcompletely submerged, provided that sufficient water is present toensure that metal dusting conditions are avoided in the heat exchanger.In some embodiments, the quench exchanger raises the bulk of the steamfor combination with the gaseous hydrocarbon stream.

In some embodiments, at least one of the heat exchangers that recoverheat from the syngas stream comprises a syngas heat recovery heatexchanger. In some embodiments, the syngas heat recovery heat exchangerexchanges heat from the syngas stream into at least one stream selectedfrom: one or more air stream, one or more fuel streams, one or morewater streams and one or more gaseous hydrocarbon streams. In someembodiments, the syngas heat recovery heat exchanger comprises amulti-stream heat exchanger. The syngas heat recovery heat exchanger maycomprise a multi-stream heat exchanger that is a multi-stream PCHE. Themulti-stream PCHE may comprise one or more syngas plates and one or morereactant feed plates, which together may be the active plates within theexchanger. The syngas plates may have multiple flow channels etched orotherwise provided thereon through which the syngas flows. The reactantfeed plates may have multiple flow channels etched or otherwise providedthereon, through which the various reactant feeds flow. For example, insome embodiments, the reactant feed plates may have one or more sets offlow channels for one or more air streams, one or more sets of flowchannels for one or more fuel streams, one or more sets of flow channelsfor one or more gaseous hydrocarbon streams and/or one or more sets offlow channels for one or more water streams. The reactant feed andsyngas plates, along with bounding plates and/or endplates may bestacked into a heat exchanger configuration. In this configuration, thePCHE may comprise a series of stacked and diffusion bonded or other wisebonded plates having multiple channels for flow of the syngas andreactant feed streams in proximity to each other to exchange heat fromthe syngas streams to the reactant feed streams. The stacking mayinclude stacking of end plates, bounding plates and specificconfigurations of syngas and reactant feed stream plates according tothe desired heat transfer. The channels on each plate may be configuredfor single or multiple pass heat transfer between the streams, and whenformed into a heat exchanger may be configured to operate in co-flow,cross-flow or counter-flow. Preferably, the syngas heat recovery heatexchanger operates in counter-flow or in a multi-pass cross-flowapproximation of counter-flow to maximize heat recovery from the syngasstream. In some embodiments, the plates for one or some of the streamsmay be configured for multiple passes, while the plates for the one orsome of the other streams are configured for single passes.

In some embodiments, the at least one heat exchangers that recovers heatfrom the syngas stream comprises a quench heat exchanger and a syngasheat recovery heat exchanger.

In some embodiments, the apparatus comprises at least one heat exchangerthat recovers heat into a water stream from a flue gas stream after theflue gas stream leaves the reformer module. In some embodiments, such aheat exchanger comprises a PCHE as described elsewhere herein, where theactive plates of the PCHE are one or more flue gas plates and one ormore water plates. In some embodiments, such as in embodiments where thereformer module is run in a reduced reforming temperature mode or in ahigher pressure reforming mode, the flue gas stream may be pre-heatedprior to entering the PCHE for exchange of heat with the water stream.Such pre-heating may include catalytic combustion of a portion of atleast one fuel stream or a portion of at least one gaseous hydrocarbonstream in the presence of the flue gas stream. The catalytic combustionmay be conducted in a flue gas pre-heater which may be configuredsubstantially the same as the air pre-heater discussed previously. Theflue gas pre-heater may be used to heat the flue gas to provideincreased heat to the water stream, thereby increasing the ratio ofsteam to carbon that is ultimately fed to the reformer module andpromoting a more favorable equilibrium for the reforming reaction for agiven pressure and temperature, making the flue gas pre-heater anattractive option for lower temperature or higher pressure reformermodules.

In some embodiments, especially embodiments where a high hydrogenconcentration is desired in the syngas stream, the apparatus may includea water-gas shift reactor. The water gas shift reactor may promotecatalytic production of hydrogen according to Equation (6).

The water-gas shift reactor preferably receives the syngas stream at atemperature sufficiently below metal dusting temperatures that the exitequilibrium temperature from the reactor is also below metal dustingtemperatures. In some embodiments, multiple water-gas shift reactors maybe used in series to further increase the hydrogen content of the syngasstream. The water-gas shift reactor may be similar to a catalyticcombustion chamber and may comprise a separate catalytic reactor or maycomprise a modified section of pipe that has been loaded with structuredor unstructured catalyst, and which preferably may include a suitableprecious metal catalyst.

In some embodiments, the apparatus is configured to avoid or reducemetal dusting conditions and coking conditions in all heat exchangers,pre-reforming stages, reforming stages and water-gas shift reactorswithin the apparatus.

In some embodiments, the apparatus for steam reforming of a gaseoushydrocarbon comprises:

a) a syngas heat recovery heat exchanger that recovers heat from asyngas stream to heat at least one air stream;

b) an air flow splitter that splits the air stream into a first airstream and a second air stream, the first air stream connecting to afuel stream to form a fuel/air mixture;

c) a fuel flow splitter that splits the fuel/air mixture into a firstfuel/air stream and a second fuel/air stream, the first fuel/air streamconnecting to a fuel pre-heater and the second fuel/air streamconnecting to an air pre-heater;

d) a fuel pre-heater that partially combusts the fuel in the firstfuel/air stream to form a heated fuel stream;

e) an air pre-heater that combusts the second fuel/air stream in thepresence of the second air stream to form a heated air stream;

f) a pre-reformer that partially reforms a heated gaseous hydrocarbonstream in the presence of steam to form a reformer stream;

g) a reformer that reforms the reformer stream to form a syngas stream;

h) a quench exchanger that recovers heat from the syngas stream to formor assist in forming steam from a water stream for the pre-reformer.

Some embodiments of the apparatus will now be detailed with reference tothe Figures. It should be understood that the apparatuses detailed areonly by way of example and that various modifications and changes to theapparatuses may be made without departing from the scope of theprocesses and apparatuses defined herein as understood by those of skillin the art. Examples of such changes may include, but are not limitedto, the type and number of reactant streams, they type and number ofeach of the heat exchangers and combustion chambers/pre-heaters, thetype, number and configurations of the pre-reforming and reformingstages, the materials of construction, the heat exchanger and pipingconfigurations and sizes, the placement and type of valves, thetemperatures and pressures in the streams, the flow-rates andcompositions of the various streams, the type and number of water-gasshift reactors if any and the catalyst types and compositions.

Referring to FIG. 1A, in some embodiments, a gaseous hydrocarbon-steamreforming system or apparatus 100 may include at least four reactantfeed streams: a gaseous hydrocarbon feed stream 102, a fuel feed stream104, an air feed stream 106 and a water feed stream 108. Gaseoushydrocarbon feed stream 102 may feed any suitable gaseous hydrocarbonstream for steam reforming, including natural gas, methane, propane,other gaseous hydrocarbons, mixtures of gaseous hydrocarbons, refineryor other flue gases and mixtures or combinations thereof into system100. Preferably, gaseous hydrocarbon feed stream 102 is sufficiently lowin impurities (such as sulfur) to provide acceptable reforming and/orwater-gas shift catalyst life. In some embodiments, gaseous hydrocarbonfeed stream 102 is natural gas or methane. Gaseous hydrocarbon feedstream 102 may enter reforming system 100 at any temperature andpressure suitable for the system. Preferably, the pressure is equal toor above the pressure of syngas stream 180 leaving the reformer module150. In some embodiments, the gaseous hydrocarbon feed stream 102 enterssystem 100 at a pressure between 10 bara and 100 bara, such as between10 bara and 90 bara, between 10 bara and 75 bara, between 10 bara and 60bara, between 10 bara and 50 bara, between 10 bara and 40 bara, between10 bara and 30 bara, between 10 bara and 20 bara, between 10 bara and 18bara, between 11 bara and 17 bara, between 12 bara and 16 bara, between13 bara and 15 bara or between 13.5 bara and 14.5 bara. In someembodiments, gaseous hydrocarbon feed stream 102 enters system 100 atany suitable temperature, such as the supply temperature or at roomtemperature, but preferably above the dew point temperature for thestream. In some embodiments, gaseous hydrocarbon feed stream 102 enterssystem 100 at a temperature between about −40° C. and 250° C., such asbetween −25 and 200° C., between −10 and 150° C., between −10° C. and100° C., between 0 and 90° C., between 0° C. and 75° C., between 5° C.and 65° C., between 10° C. and 50° C., between 15° C. and 40° C.,between 15° C. and 35° C., between 20° C. and 30° C. or between 20° C.and 25° C.

Fuel feed stream 104 may be any suitable combustion fuel feed stream forsteam reforming processes, such as off-gas or tail streams from apressure swing adsorption process (PSA), from a methanol productionprocess or from an ammonia production process and may include or beenriched with other fuel components such as a gaseous hydrocarbonstream, or streams such as natural gas streams, methane streams, propanestreams, mixtures of gaseous hydrocarbons, refinery or other flue gasesand mixtures or combinations thereof. In some embodiments, a portion ofgaseous hydrocarbon feed stream 102 or another gaseous hydrocarbonstream may be provided as at least a portion of fuel feed stream 104. Insome embodiments, fuel feed stream 104 may include residual gaseoushydrocarbons and/or hydrogen from syngas stream 192 after downstreamprocessing. Fuel feed stream 104 may enter reforming system 100 at anytemperature and pressure suitable for the system. In some embodiments,such as embodiments when fuel feed stream 104 comprises a PSA off-gas ortail stream, fuel feed stream 104 enters system 100 at a pressure lessthan 10 barg, such as less than 8 barg, less than 5 barg, less than 2.5barg, less than 1 barg, less than 0.75 barg, less than 0.5 barg, lessthan 0.4 barg, less than 0.3 barg, less than 0.2 barg, less than 0.15barg, less than 0.10 barg or less than 0.075 barg. In some embodiments,such as when fuel feed stream 104 comprises a methanol synthesis purge,fuel feed stream 104 may enter the system at a pressure that issubstantially higher, in which case, the pressure may be stepped downusing any suitable means for stepping down pressures of gaseous streams.In some embodiments, fuel feed stream 104 enters system 100 at anysuitable temperature, such as the supply temperature or at roomtemperature, but preferably above the dew point of the stream. In someembodiments, fuel feed stream 104 enters system 100 at a temperaturebetween −40° C. and 350° C., such as between −30° C. and 300° C.,between −20° C. and 250° C., between −10° C. and 200° C., between −5° C.and 150° C., between 0° C. and 100° C., between 0° C. and 50° C.,between 5° C. and 40° C., between 10° C. and 35° C., between 15° C. and30° C. or between 20° C. and 25° C.

Air feed stream 106 may be any suitable air feed stream, such as aforced air feed stream or a compressed air feed stream, that providessufficient oxygen for combustion processes within the reforming system100. In some embodiments, the air feed stream may be enriched withadditional oxygen or may be purified to remove or limit the presence ofone or more particulate or gaseous components or contaminants. In someembodiments, air feed stream 106 enters system 100 at a pressure lessthan 1 barg, such as less than 0.75 barg, less than 0.50 barg, less than0.40 barg, less than 0.30 barg, less than 0.20 barg, less than 0.15barg, less than 0.10 barg or less than 0.075 barg. In some embodiments,air feed stream 106 enters system 100 at any suitable temperature, suchas the supply temperature or at room temperature, but preferably abovethe stream's dew point temperature. In some embodiments, air feed stream106 enters system 100 at a temperature between −40° C. and 350° C., suchas between −30° C. and 300° C., between −20° C. and 250° C., between−10° C. and 200° C., between −5° C. and 150° C., between 0° C. and 100°C., between 0° C. and 50° C., between 5° C. and 40° C., between 10° C.and 35° C., between 15° C. and 30° C. or between 20° C. and 25° C.

Water feed stream 108 may be any suitable water feed stream and may bean untreated, a treated, a purified or a conditioned water stream.Preferably, the water has been treated to meet at least boiler feedwaterstandards appropriate for the operating temperatures and pressures toavoid scale formation within the heat exchangers and/or excessiveblowdown requirements. In some embodiments, water feed stream 108, mayhave been heated above ambient temperature in a water heater or boilerprior to entering the process. In some embodiments, water feed stream108 may comprise steam produced outside of the process, in which case itmay be directly mixed with gaseous hydrocarbon stream 102 just prior toentering the reformer module 150, in which case the heat exchangeconfiguration for FIG. 1A may be changed. Preferably, all of thenecessary steam is generated within the process from water stream 108with no steam export from the process or import into the process. Insome embodiments, water feed stream 108 enters system 100 at anysuitable pressure above the pressure of syngas stream 180 leaving thereformer module, such as between 10 bara and 100 bara, such as between10 bara and 90 bara, between 10 bara and 75 bara, between 10 bara and 60bara, between 10 bara and 50 bara, between 10 bara and 40 bara, between10 bara and 30 bara, between 10 bara and 20 bara, between 10 bara and 18bara, between 11 bara and 17 bara, between 12 bara and 16 bara, between13 bara and 15 bara or between 13.5 bara and 14.5 bara. In someembodiments, water feed stream 108 enters system 100 at any suitabletemperature, such as the supply temperature or at room temperature. Insome embodiments, water feed stream 108 enters system 100 at atemperature just above freezing and below boiling, such as between 0.1°C. and 350° C., between 2.5° C. and 250° C., between 5° C. and 150° C.,between 10° C. and 125° C., between 15° C. and 100° C., between 15° C.and 75° C., between 15° C. and 50° C., between 15° C. and 40° C.,between 15° C. and 35° C., between 20° C. and 30° C. or between 20° C.and 25° C. Water feed stream 108 may be pre-heated in heat exchanger 109which may be separate from or may be part of syngas heat recovery heatexchanger 110. In some embodiments, heat exchanger 109 is combined withsyngas heat recovery heat exchanger 110 in a single PCHE.

One or more of the reactant feed streams, such as from 2 to 10, 3 to 9or 4 to 6 reactant feed streams or 2, 3, 4, 5, 6, 7, 8, 9 or 10 reactantfeed streams, may be pre-heated in one or more syngas heat recovery heatexchangers 110. In some embodiments, at least one air feed stream, suchas air feed stream 106 or air feed stream 107 is pre-heated in exchanger110. In other embodiments and as shown, exchanger 110 may be amulti-stream heat exchanger where more than one reactant feed stream ispre-heated.

In some embodiments, including the embodiment as shown in FIG. 1A, fuelfeed stream 104 optionally may be split via fuel stream splitter 113into fuel feed stream 105 and flue gas fuel stream 112 prior to enteringsyngas heat recovery heat exchanger 110. Both streams 105 and 112 maythen be heated in syngas heat recovery heat exchanger 110.Alternatively, fuel feed stream 104 may be split after leaving exchanger110, but preferably prior to combining with combustion air stream 114.Fuel feed stream 104 may be split using any suitable means of splittingthe flow, either before or after the syngas heat recovery heat exchanger110, such as a “T” or “Y” piping connection, and may be split to divertsufficient fuel from fuel feed stream 104 via flue gas fuel stream 112for combustion in the presence of flue gas stream 160 to provideadditional heat to water feed stream 108. Fuel stream splitter 113 maybe a piping junction or any other suitable flow splitting mechanism, mayinclude a valve 113 a as shown, or other suitable splitting device forcontrolling flow of the fuel, may be split and the flow controlled usingpassive means which maintain the desired downstream fuel/air ratio forfeed to fuel pre-heater 120, air pre-heater 122, and flue gas pre-heater175 throughout a broad range of flow magnitudes. Such passive means mayinclude control of the flow path geometry based on pressure drops and adesired Reynolds number range within the relevant flow paths.

Similarly, in some embodiments, including the embodiment as shown inFIG. 1A, air feed stream 106 may be split into air feed stream 107 andcombustion air stream 114 prior to entering syngas heat recovery heatexchanger 110 via air flow splitter 115. Both streams 107 and 114 maythen be heated in syngas heat recovery heat exchanger 110. In someembodiments, exchanger 110 is configured such that combustion air stream114 combines with fuel feed stream 105 in exchanger 110 to form fuel/airmixture stream 118 prior to exiting the exchanger. Alternatively, airfeed stream 106 may be split after leaving exchanger 110. Air flowsplitter 115 may be any suitable means of splitting the flow of air feedstream 106 either before or after the syngas heat recovery heatexchanger 110, such as a “T” or “Y” piping connection, as long ascombustion air stream 114 connects with the fuel feed stream 105 priorto the fuel/air flow splitter 116. The air flow splitter 115 divertssufficient air from air feed stream 106 via combustion air stream 114into fuel feed stream 105, preferably prior to the fuel/air flowsplitter 116 to form a fuel/air mixture stream 118 with sufficient airfor partial combustion of fuel from fuel feed stream 105 in the fuelpre-heater 120. Air flow splitter 115 may be a piping junction or anyother suitable flow splitting mechanism, may include a valve 115 a asshown, or other suitable splitting and control device, or the air flowmay be split and the flow controlled using passive means which maintainthe desired downstream fuel/air ratio for feed to fuel pre-heater 120and air pre-heater 122 throughout a broad range of flow magnitudes. Suchpassive means may include control of the flow path geometry based onpressure drops and a desired Reynolds number range within the relevantflow paths.

The syngas heat recovery heat exchanger 110 may be any suitable heatexchanger and may exchange heat between the entering hot and coldstreams using co-flow, counter-flow or cross-flow heat exchange.Preferably, the syngas heat recovery heat exchanger is a PCHE andexchanges heat using counter-flow heat exchange or an approximation tocounter-flow heat exchange using multi-pass cross flow exchange in anoverall counter-flow direction. In some embodiments, the syngas heatrecovery heat exchanger recovers heat from the syngas stream before itexits the reformer system 100 for further processing, such as, forexample, in a pressure swing adsorption system, a membrane separationsystem, a methanol production system or in an ammonia production system.The syngas heat recovery heat exchanger 110 may recover heat from thesyngas stream 190 to preheat one or more reactant feed streams,including one or more gaseous hydrocarbon streams, one or more fuelstreams, one or more air streams, and/or one or more water streams. Inorder to avoid or reduce metal dusting, the syngas stream 190 preferablyenters the heat exchanger 110 at a temperature that is below the metaldusting temperature. Preferably the syngas stream 190 leaves the heatexchanger 110 at a temperature and pressure suitable for any furtherdownstream processing.

In some embodiments, the syngas heat recovery heat exchanger 110 maycomprise a PCHE that is constructed from a series of plates as shown inFIG. 2A-C. The plates may be combined into a stack and diffusion bondedor otherwise bonded to one another to provide heat exchange between theentering hot and cold streams. In general the flow paths for each of thestreams may be formed in the plates by etching, milling or othersuitable process and may be configured to provide for the desired heatexchange, while limiting pressure drop for one or more streams acrossthe heat exchanger. Preferably, the entering syngas stream 190 is belowmetal dusting temperatures thereby ensuring that metal dustingconditions are avoided within syngas heat recovery heat exchanger 110.

Referring to FIG. 2A-C, in some embodiments, syngas heat recovery heatexchanger 110 may comprise one or more bounding plates 210, one or moresyngas plates 230 and one or more reactant feed plates 260. In theembodiment shown in FIG. 2A-C, the plates in conjunction with suitableendplates (not shown), when appropriately stacked and formed into a heatexchanger, will form a syngas heat recovery heat exchanger 110 thatincludes heat exchanger 109. Each of the plates may be constructed frommaterials suitable for the purpose and the conditions present inexchanger 110. Examples of suitable materials for constructing plates210, 230 and 260 include 316 stainless steel and 304 stainless steel andthe plates may independently have the thicknesses described in Table 1.In some embodiments, the plates may each be 1.6 mm thick.

FIG. 2A shows a bounding plate 210 having a syngas flow path 211comprising at least one flow channel 212 connecting syngas inlets 213with syngas outlets 214. Bounding plates 210 ensures that all of thereactant feed plates 260 have hot stream plates on both sides, either abounding plate 210 or a syngas plate 230 and help to balance the heatload and heat flux throughout the height of the stack. Bounding plate210 may have one or more independent flow channels 212, which withadjacent ridges may be sized to provide for safe pressure containmentand a cost effective combination of heat transfer capacity and pressuredrop. In some embodiments, independent flow channels 212 may eachcomprise a generally semicircular cross-section and may have thedimensions described in Table 1. In some embodiments, independent flowchannels 212 may each have a semicircular cross-section with a width ofabout 1.95 mm, a depth of about 1.10 mm and about 0.4 mm ridges. Thougha specific number of independent flow channels 212 are shown, it shouldbe understood that syngas flow path 211 may comprise any suitable numberof independent flow channels configured appropriately according to theindividual needs of the system.

Though FIG. 2A shows syngas flow path 211 as a multi-pass flow path,flow path 211 may also comprise a direct counter flow, co-flow, crossflow or single pass flow path comprising multiple independent channels.In some embodiments syngas flow path 211 may comprise more than onepass, each pass comprising a single reversal in flow direction, such asfrom 2 to 100 passes, 5 to 75 passes, 10 to 60 passes, 15 to 50 passesor 20 to 40 passes. Preferably, syngas flow path 211 comprises amulti-loop flow path having 5 passes or greater, 10 passes or greater,15 passes or greater, 20 passes or greater, 25 passes or greater or 30passes or greater where the passes are in cross flow during heatexchange and where the syngas flows in a generally counter-flowdirection relative to the flows on the reactant feed plate 260.

Bounding plate 210 also includes air feed stream penetrations 215 and216, combustion air stream penetration 217, fuel feed stream penetration218, fuel/air mixture stream penetration 227, flue gas fuel streampenetrations 219 and 220, gaseous hydrocarbon feed stream penetrations221 and 222, syngas stream penetrations 223 and 224 and water streampenetrations 225 and 226.

Referring to FIG. 2B, syngas plate 230 includes syngas inlets 231,syngas outlets 232 and syngas flow path 233. Syngas flow path 233 maycomprise one or multiple syngas independent flow channels 234. Thechannels 234 and adjacent ridges may be sized to provide for safepressure containment and a cost effective combination of heat transfercapacity and pressure drop. In some embodiments, syngas independent flowchannels 234 may each comprise a generally semicircular cross-sectionand may have the dimensions described in Table 1. In some embodiments,independent flow channels 234 may each have a semicircular cross-sectionwith a width of about 1.95 mm, a depth of about 1.10 mm and 0.4 mmridges. Though a specific number of independent flow channels 234 areshown, it should be understood that syngas flow path 233 may compriseany suitable number of independent flow channels configuredappropriately according to the individual needs of the system.

Though FIG. 2B shows syngas flow path 233 as a multi-pass flow path,flow path 233 may also comprise a direct counter flow, co-flow, crossflow or single pass flow path comprising multiple independent channels.In some embodiments syngas flow path 233 may comprise more than onepass, each pass comprising a single reversal in flow direction, such asfrom 2 to 100 passes, 5 to 75 passes, 10 to 60 passes, 15 to 50 passesor 20 to 40 passes. Preferably, syngas flow path 233 comprises acounter-flow flow path which may be approximated by a multi-pass flowpath having 5 passes or greater, 10 passes or greater, 15 passes orgreater, 20 passes or greater, 25 passes or greater or 30 passes orgreater where the passes are in cross flow during heat exchange, but thesyngas flows in a generally cross flow or counter-flow directionrelative to the air, fuel and gaseous hydrocarbon flows on the reactantfeed plate 260.

Syngas plate 230 also includes air feed stream penetrations 235 and 236,combustion air stream penetration 237, fuel feed stream penetration 238,fuel/air mixture stream penetration 247, flue gas fuel streampenetrations 239 and 240, gaseous hydrocarbon feed stream penetrations241 and 242, syngas stream penetrations 243 and 244 and water streampenetrations 245 and 246.

Referring to FIG. 2C, reactant feed plate 260 has a water stream flowpath 261 which connects water stream inlets 262 and water stream outlets263 as shown in the lower left portion of the reactant feed plate 260.Water stream flow path 261 may comprise one or multiple independent flowchannels 264. This portion of reactant feed plate 260, when formed intoa heat exchanger corresponds to the water flow streams for heatexchanger 109 as indicated in FIG. 1A. Flow channels 264 and adjacentridges may be sized to provide for safe pressure containment and a costeffective combination of heat transfer capacity and pressure drop. Insome embodiments, independent flow channels 264 may each comprise agenerally semicircular cross-section and may have the dimensionsdescribed in Table 1. In some embodiments, independent flow channels 264may each have a semicircular cross-section with a width of about 1.90mm, a depth of about 1.10 mm and about 0.4 mm ridges. Though a specificnumber of independent flow channels 264 are shown, it should beunderstood that water stream flow path 261 may comprise any suitablenumber of independent flow channels configured appropriately accordingto the individual needs of the system.

Though FIG. 2C shows water stream flow path 261 as a multi-pass flowpath, flow path 261 may also comprise a direct counter flow, co-flow,cross flow or single pass flow path comprising multiple independentchannels. In some embodiments water stream flow path 261 may comprisemore than one pass, each pass comprising a single reversal in flowdirection, such as from 2 to 100 passes, 5 to 75 passes, 10 to 60passes, 15 to 50 passes or 20 to 40 passes. Preferably, water streamflow path 261 comprises a multi-pass flow path having 5 passes orgreater, 10 passes or greater, 15 passes or greater, 20 passes orgreater, 25 passes or greater or 30 passes or greater where the passesare in cross flow during heat exchange, but flow in a generallycounter-flow direction relative to the flow of the syngas stream.

Reactant feed plate 260 also includes air feed flow path 265 with airfeed inlet 266 and air feed outlet 267, combustion air feed flow path268, with combustion air feed inlet 269, fuel feed flow path 270 withfuel feed inlet 271 and fuel/air mixture outlet 272, flue gas fuel flowpath 273 with flue gas fuel inlet 274 and flue gas fuel outlet 275 andgaseous hydrocarbon flow path 276 with gaseous hydrocarbon inlet 277 andgaseous hydrocarbon outlet 278. Each of flow paths 265, 268, 270, 273and 276 may comprise one or multiple independent flow channels 279, 280,281, 282 and 283 respectively. In general, each of independent flowchannels 279, 280, 281, 282 and 283 and adjacent ridges may be sized toprovide for safe pressure containment and a cost effective combinationof heat transfer capacity and pressure drop. In some embodiments,independent flow channels 279, 280, 281, 282 and 283 may eachindependently comprise a generally semicircular cross-section and mayeach independently have the dimensions described in Table 1. In someembodiments, independent flow channels 279, 280, 281, 282 and 283 mayeach have a semicircular cross-section with a width of about 1.90 mm, adepth of about 1.10 mm and about 0.4 mm ridges. In some embodiments theinlet and outlet portions of independent flow channels 283 may each havea semicircular cross-section with a width of about 1.75 mm, a depth ofabout 1.00 mm and 0.5 mm ridges. Though a specific number of independentflow channels 279, 280, 281, 282 and 283 are shown, it should beunderstood that flow paths 265, 268, 270, 273 and 276 may independentlycomprise any suitable number of independent flow channels configuredappropriately according to the individual needs of the system.

Though FIG. 2C shows flow paths 265, 268, 270, 273 and 276 as directcross flow or single pass flow paths, in some embodiments flow paths265, 268, 270, 273 and 276 may independently comprise more than onepass, each pass comprising a single reversal in flow direction, such asfrom 2 to 20 passes, 2 to 10 passes or 2 to 5 passes. Preferably, flowpaths 265, 268, 270, 273 and 276 each comprise a direct or single passcross flow flow path. In FIG. 2C, combustion air flow path 268 isconfigured to provide for mixing the combustion air stream 114 of FIG.1A, with fuel feed stream 105 inside exchanger 110 by directing airflowing through flow path 268 and fuel flowing in flow path 270 to thesame outlet, fuel/air mixture outlet 272. When configured in thismanner, there is no separate joining of these streams downstream ofsyngas heat recovery heat exchanger 110 as is depicted in FIG. 1A.

Reactant feed plate 260 also includes air feed stream penetrations 285and 286, combustion air stream penetration 287, fuel feed streampenetration 288, fuel/air mixture stream penetration 289, flue gas fuelstream penetrations 290 and 291, gaseous hydrocarbon feed streampenetrations 292 and 293, syngas stream penetrations 294 and 295 andwater stream penetrations 296 and 297.

In some embodiments, the plates used to form embodiments of syngas heatrecovery heat exchanger 110 may be stacked and diffusion bonded orotherwise bonded in any suitable order to form a heat exchanger. In someembodiments, the plates may be stacked and diffusion bonded or otherwisebonded in order as follows: at least one 1 end plate (not shown), 1bounding plate 210, multiple heat exchange cells, each heat exchangecell comprising a reactant feed plate 260 followed by a syngas plate230, 1 additional reactant feed plate 260, 1 bounding plate 210, and atleast 1 end plate (not shown). Accordingly, in some embodiments theorder of printed circuit heat exchange plates in a given stack may havethe following pattern (Endplate=“E”, bounding plate 210=“B”, reactantfeed plate 260=“R”, syngas feed plate 230=“S”): E B R S R S R S . . . RS R B E. The end plates may be blank plates with no flow path circuitryand may be insulated to enhance heat transfer and limit heat loss. Theend plates may serve as lids to the chambers and flow access pathsformed by alignment of the penetrations and support connection of therelevant streams to heat exchanger 110, such as via ports or headers influid connection with the chambers and flow paths. Accordingly, theendplates should be thick enough to accommodate the pressures in each ofthe penetrations and to support the ports or headers. In someembodiments, a single endplate is used for each end of the exchanger164, where the endplate is thicker than the other plates. In otherembodiments, multiple endplates may be used at each end to providesufficient thickness to support or provide for the headers or ports.

In some embodiments, syngas heat recovery heat exchanger 110 comprisesfrom 5 to 30 heat exchange cells, such as from 7-25, from 8-20, from 9to 17 or from 10 to 15 heat exchange cells, each heat exchange cellcomprising a reactant feed plate 260 and a syngas plate 230. Inpreferred embodiments for reforming 2 SCMH of natural gas using PSAoff-gas as fuel, syngas heat recovery heat exchanger 110 comprises atleast 14 heat exchange cells. In one preferred embodiment, syngas heatrecovery heat exchanger 110 comprises 2 bounding plates 210, 14 heatexchange cells, an additional reactant feed plate 260 and 5 endplatesand comprises plates that are each 1.65 mm thick giving a stack that is57.75 mm tall. The number of plates and heat exchange cells may bemodified according to production needs, heat exchange efficiency, numberof feed streams and other parameters.

When the various plates are stacked and diffusion bonded or otherwisebonded to form a heat exchanger, preferably the various correspondingpenetrations on each of the plates are aligned to form flow access pathsor chambers for the various reactant feeds. In some embodiments, airfeed stream penetrations 215, 235 and 285 and 216, 236 and 286 arealigned to form access flow paths or chambers through which air feedstream 107 may be supplied to and may exit, respectively, from thereactant feed plates 260 of the heat exchanger. In some embodiments,combustion air stream penetrations 217, 237 and 287 are aligned to formaccess flow paths or chambers through which combustion air stream 114may be supplied to the reactant feed plates 260 of the heat exchanger.In some embodiments, fuel feed stream penetrations 218, 238 and 288 arealigned to form access flow paths or chambers through which fuel feedstream 105 may be supplied to the reactant feed plates 260 of the heatexchanger. In some embodiments, fuel/air mixture stream penetrations227, 247 and 289 are aligned to form access flow paths or chambersthrough which fuel feed stream 107 in combination with combustion airstream 114 may exit the reactant feed plates 260 of the heat exchanger.In some embodiments, flue gas feed stream penetrations 219, 239 and 290and 220, 240 and 291 are aligned to form access flow paths or chambersthrough which flue gas fuel stream 112 may be supplied to and may exit,respectively, the reactant feed plates 260 of the heat exchanger. Insome embodiments, gaseous hydrocarbon feed stream penetrations 221, 241and 292 and 222, 242 and 293 are aligned to form access flow paths orchambers through which gaseous hydrocarbon feed stream 102 may besupplied to and may exit, respectively, the reactant feed plates 260 ofthe heat exchanger. In some embodiments syngas gas stream penetrations213, 231 and 294 and 224, 244 and 295 are aligned to form access flowpaths or chambers through which syngas stream 190 may be supplied to andmay exit, respectively, the syngas plates 230 and bounding plates 210 ofthe heat exchanger. In some embodiments, water feed stream penetrations225, 245 and 277 and 226, 246 and 296 are aligned to form access flowpaths or chambers through which water feed stream 108 may be supplied toand may exit, respectively, the reactant feed plates 260 of the heatexchanger.

In addition to aligning the various penetrations, the stacking of theplates preferably places the independent channels making up flow paths265, 268, 270, 273 and 276 in close proximity to the independentchannels making up flow paths 211 and/or 233 to facilitate heat transferbetween the relevant streams through the walls of the respectiveindependent channels.

In operation, gaseous hydrocarbon stream 102 may enter syngas heatrecovery heat exchanger 110 at essentially the pressure and temperatureit enters the reformer system 100 and may leave exchanger 110 at apressure between 10 bara and 100 bara, such as between 10 bara and 90bara, between 10 bara and 75 bara, between 10 bara and 60 bara, between10 bara and 50 bara, between 10 bara and 40 bara, between 10 bara and 30bara, between 10 bara and 20 bara, between 10 bara and 18 bara, between11 bara and 17 bara, between 12 bara and 16 bara, between 13 bara and 15bara or between 13.5 bara and 14.5 bara and at a temperature between200° C. and 375° C., such as between 225° C. and 375° C., between 250°C. and 370° C., between 275 and 365° C., between 300 and 360° C. orbetween 325° C. and 355° C. Preferably, the temperature of stream 102leaving syngas heat recovery heat exchanger 110 is within 100° C. of thetemperature of syngas stream 190, such as within 90° C., 80° C., 70° C.,60° C. 50° C., 40° C. 30° C. or within 20° C. of the temperature ofsyngas steam 190. Preferably the pressure drop for gaseous hydrocarbonstream 102 across exchanger 110 is less than 0.50 bara, such as forexample, less than 0.40 bara, less than 0.30 bara, less than 0.20 baraor less than 0.10 bara.

In some embodiments, fuel feed stream 105 may enter syngas heat recoveryheat exchanger 110 at a pressure less than 10 barg, such as less than 8barg, less than 5 barg, less than 2.5 barg, less than 1 barg, less than0.75 barg, less than 0.5 barg, less than 0.4 barg, less than 0.3 barg,less than 0.2 barg, less than 0.15 barg, less than 0.10 barg or lessthan 0.075 barg. In some embodiments, fuel feed stream 105 enters syngasheat recovery heat exchanger 110 at any suitable temperature, such asthe supply temperature or at room temperature. In some embodiments, fuelfeed stream 105 enters syngas heat recovery heat exchanger 110 at atemperature between −40° C. and 350° C., such as between −30° C. and300° C., between −20° C. and 250° C., between −10° C. and 200° C.,between −5° C. and 150° C., between 0° C. and 100° C., between 0° C. and50° C., between 5° C. and 40° C., between 10° C. and 35° C., between 15°C. and 30° C. or between 20° C. and 25° C. In some embodiments, fuelfeed stream 105 may leave exchanger 110 at a pressure less than 10 barg,such as less than 8 barg, less than 5 barg, less than 2.5 barg, lessthan 1 barg, less than 0.75 barg, less than 0.5 barg, less than 0.4barg, less than 0.3 barg, less than 0.2 barg, less than 0.15 barg, lessthan 0.10 barg or less than 0.075 barg and at a temperature between 200°C. and 375° C., such as between 225° C. and 375° C., between 250° C. and370° C., between 275 and 365° C., between 300 and 360° C. or between325° C. and 355° C. Preferably, the temperature of stream 105 leavingsyngas heat recovery heat exchanger 110 is within 100° C. of thetemperature of syngas stream 190, such as within 90° C., 80° C., 70° C.,60° C. 50° C., 40° C. 30° C. or within 20° C. of the temperature ofsyngas steam 190. Preferably the pressure drop for fuel feed stream 105across exchanger 110 is less than 0.10 bar, such as less than 0.09 bar,less than 0.07 bar, less than 0.06 bar or less than 0.05 bar.

Flue gas fuel stream 112 may enter syngas heat recovery heat exchanger110 at a pressure less than 10 barg, such as less than 8 barg, less than5 barg, less than 2.5 barg, less than 1 barg, less than 0.75 barg, lessthan 0.5 barg, less than 0.4 barg, less than 0.3 barg, less than 0.2barg, less than 0.15 barg, less than 0.10 barg or less than 0.075 bargand at any suitable temperature, such as at the supply temperature or atroom temperature, or such as at a temperature between −40° C. and 350°C., such as between −30° C. and 300° C., between −20° C. and 250° C.,between −10° C. and 200° C., between −5° C. and 150° C., between 0° C.and 100° C., between 0° C. and 50° C., between 5° C. and 40° C., between10° C. and 35° C., between 15° C. and 30° C. or between 20° C. and 25°C. In some embodiments, flue gas fuel stream 112 may leave exchanger 110at a pressure less than 10 barg, such as less than 8 barg, less than 5barg, less than 2.5 barg, less than 1 barg, less than 0.75 barg, lessthan 0.5 barg, less than 0.4 barg, less than 0.3 barg, less than 0.2barg, less than 0.15 barg, less than 0.10 barg or less than 0.075 bargand at a temperature between 200° C. and 375° C., such as between 225°C. and 375° C., between 250° C. and 370° C., between 275 and 365° C.,between 300 and 360° C. or between 325° C. and 355° C. Preferably, thetemperature of stream 112 leaving syngas heat recovery heat exchanger110 is within 100° C. of the temperature of syngas stream 190, such aswithin 90° C., 80° C., 70° C., 60° C. 50° C., 40° C. 30° C. or within20° C. of the temperature of syngas steam 190. Preferably the pressuredrop for flue gas fuel stream 112 across exchanger 110 is less than 0.10bar, such as less than 0.09 bar, less than 0.07 bar, less than 0.06 baror less than 0.05 bar.

Combustion air stream 114 may enter syngas heat recovery heat exchanger110 at a pressure less than 1 barg, such as less than 0.75 barg, lessthan 0.50 barg, less than 0.40 barg, less than 0.30 barg, less than 0.20barg, less than 0.15 barg, less than 0.10 barg or less than 0.075 bargand at any suitable temperature, such as at the supply temperature or atroom temperature, or such as at a temperature between −40° C. and 350°C., such as between −30° C. and 300° C., between −20° C. and 250° C.,between −10° C. and 200° C., between −5° C. and 150° C., between 0° C.and 100° C., between 0° C. and 50° C., between 5° C. and 40° C., between10° C. and 35° C., between 15° C. and 30° C. or between 20° C. and 25°C. In some embodiments, combustion air stream 114 may leave exchanger110 at a pressure less than 1 barg, such as less than 0.75 barg, lessthan 0.50 barg, less than 0.40 barg, less than 0.30 barg, less than 0.20barg, less than 0.15 barg, less than 0.10 barg or less than 0.075 bargand at a temperature between 200° C. and 375° C., such as between 225°C. and 375° C., between 250° C. and 370° C., between 275 and 365° C.,between 300 and 360° C. or between 325° C. and 355° C. Preferably, thetemperature of stream 114 leaving syngas heat recovery heat exchanger110 is within 100° C. of the temperature of syngas stream 190, such aswithin 90° C., 80° C., 70° C., 60° C. 50° C., 40° C. 30° C. or within20° C. of the temperature of syngas steam 190. Preferably, the pressuredrop for combustion air stream 114 across exchanger 110 is less than0.10 bar, such as less than 0.09 bar, less than 0.07 bar, less than 0.06bar or less than 0.05 bar.

Air feed stream 107 may enter syngas heat recovery heat exchanger 110 ata pressure less than 1 barg, such as less than 0.75 barg, less than 0.50barg, less than 0.40 barg, less than 0.30 barg, less than 0.20 barg,less than 0.15 barg, less than 0.10 barg or less than 0.075 barg and atany suitable temperature, such as at the supply temperature or at roomtemperature, or such as at a temperature between −40° C. and 350° C.,such as between −30° C. and 300° C., between −20° C. and 250° C.,between −10° C. and 200° C., between −5° C. and 150° C., between 0° C.and 100° C., between 0° C. and 50° C., between 5° C. and 40° C., between10° C. and 35° C., between 15° C. and 30° C. or between 20° C. and 25°C. In some embodiments, air feed stream 107 may leave exchanger 110 at apressure less than 1 barg, such as less than 0.75 barg, less than 0.50barg, less than 0.40 barg, less than 0.30 barg, less than 0.20 barg,less than 0.15 barg, less than 0.10 barg or less than 0.075 barg and ata temperature between 200° C. and 375° C., such as between 225° C. and375° C., between 250° C. and 370° C., between 275 and 365° C., between300 and 360° C. or between 325° C. and 355° C. Preferably, thetemperature of stream 107 leaving syngas heat recovery heat exchanger110 is within 100° C. of the temperature of syngas stream 190, such aswithin 90° C., 80° C., 70° C., 60° C. 50° C., 40° C. 30° C. or within20° C. of the temperature of syngas steam 190. Preferably, the pressuredrop for air feed stream 107 across exchanger 110 is less than 0.10 bar,such as less than 0.09 bar, less than 0.07 bar, less than 0.06 bar orless than 0.05 bar.

Syngas stream 190 may enter syngas heat recovery heat exchanger 110 at atemperature of between 200° C. and 450° C., such as between 300° C. and420° C., between 325° C. and 400° C., between 350° C. and 400° C.,between 375° C. and 400° C., between 385° C. and 400° C. or between 385°C. and 395° C. and at a pressure below the pressure of syngas stream 180leaving reformer module 150, such as between 10 bara and 100 bara,between 10 bara and 90 bara, between 10 bara and 75 bara, between 10bara and 60 bara, between 10 bara and 50 bara, between 10 bara and 40bara, between 10 bara and 30 bara, between 10 bara and 20 bara, between10 bara and 18 bara, between 11 bara and 17 bara, between 12 bara and 16bara, between 13 bara and 15 bara or between 13.5 bara and 14.5 bara andmay leave exchanger 110 at a temperature of between 75° C. and 200° C.,between 100° C. and 180° C., between 125° C. and 170° C. or between 130°C. and 150° C. and at a pressure between 10 bara and 100 bara, such asbetween 10 bara and 90 bara, between 10 bara and 75 bara, between 10bara and 60 bara, between 10 bara and 50 bara, between 10 bara and 40bara, between 10 bara and 30 bara, between 10 bara and 20 bara, between10 bara and 18 bara, between 11 bara and 17 bara, between 12 bara and 16bara, between 13 bara and 15 bara or between 13.5 bara and 14.0 bara.Preferably, the pressure drop for syngas stream 114 across exchanger 110is less than 0.50 bar, such as for example, less than 0.40 bar, lessthan 0.30 bar, less than 0.20 bar or less than 10 bar.

Syngas stream 191 leaving syngas heat recovery heat exchanger 110 mayproceed to heat exchanger 109, where it may exchange heat with waterstream 108. Preferably, heat exchanger 109 is combined with heatexchanger 110 into a single PCHE. Syngas stream may enter heat exchanger109 (whether as a portion of heat exchanger 109 or separately) at thetemperature and pressure that it left heat exchanger 110 and may leaveexchanger 109 at a temperature of between 75° C. and 200° C., between100° C. and 180° C., between 125° C. and 170° C. or between 130° C. and150° C. and at a pressure of between 10 bara and 100 bara, between 10bara and 90 bara, between 10 bara and 75 bara, between 10 bara and 60bara, between 10 bara and 50 bara, between 10 bara and 40 bara, between10 bara and 30 bara, between 10 bara and 20 bara, between 10 bara and 18bara, between 11 bara and 17 bara, between 12 bara and 16 bara, between13 bara and 15 bara or between 13.5 bara and 14.5 bara. Preferably,water stream 108 leaves heat exchanger 109 within 20° C. of the inlettemperature of syngas stream 191.

Water stream 108 may enter heat exchanger 109 (whether as a portion ofheat exchanger 110 or separately) at essentially the temperature andpressure that it enters system 100 and may leave heat exchanger 109 at atemperature of between 95° C. and 200° C., such as between 110° C. and190° C., between 115° C. and 180° C., between 120° C. and 170° C. orbetween 130° C. and 150° C. and at a pressure equal to or above thepressure of stream 180 leaving reformer module 150, such as between 10bara and 100 bara, between 10 bara and 90 bara, between 10 bara and 75bara, between 10 bara and 60 bara, between 10 bara and 50 bara, between10 bara and 40 bara, between 10 bara and 30 bara, between 10 bara and 20bara, between 10 bara and 18 bara, between 11 bara and 17 bara, between12 bara and 16 bara, between 13 bara and 15 bara or between 13.5 baraand 14.5 bara.

Combustion air stream 114 may be combined with fuel feed stream 105inside syngas heat recovery heat exchanger 110 or after leaving heatexchanger 110 as shown in FIG. 1A to form fuel/air mixture stream 118and fuel air mixture stream 118 may be split via fuel/air flow splitter116 into fuel preheat mixture 119 and air preheat mixture 117. Fuel/airflow splitter 116 may be a piping junction or any other suitable flowsplitting mechanism, may include a valve, or other suitable splittingdevice for controlling flow or the fuel/air flow may be split and theflow controlled using passive means which maintain the desireddownstream fuel/air ratio for feed to fuel pre-heater 120 and airpre-heater 122 throughout a broad range of flow magnitudes.

Alternatively, in some embodiments, the details of the configuration ofthe fuel and air streams entering and leaving the syngas heat recoveryheat exchanger and proceeding to the pre-heaters may appear as in FIG.1B. FIG. 1B shows fuel feed stream 105, combustion air stream 114 andair feed stream 107 entering a portion of syngas heat recovery heatexchanger 110. In FIG. 1B, combustion air stream 114 does not combinewith fuel feed stream 105 prior to entering fuel pre-heater 120 andinstead joins with fuel preheat stream 119 a, which is not an air/fuelmixture in this embodiment, at pre-heater 120. In such a case fuel feedstream 105 may be split into air preheat fuel stream 117 a and fuelpreheat stream 119 a, with neither stream including air from combustionair stream 114, and fuel stream 117 a may be fed as a pure fuel streaminto air pre-heater 122. In such a case, the details of the resistancenetwork and the pressure balances in FIG. 15 would be slightlydifferent. In some embodiments, such as embodiments where the hydrogenand carbon monoxide content of the fuel streams is sufficient forcatalytic combustion, pre-heaters 120 and 122 may be configured to mixthe entering air and pure fuel streams prior to passing the mixed streamto the catalyst beds or chambers for catalytic combustion.Alternatively, pre-heaters 120 and 122 may be configured with anignition source for start-up, such as a spark source or a heatingelement, to provide for non-catalytic (homogeneous) combustion of all orat least a portion of the fuel stream. In such cases at least a portionof the non-catalytic combustion would need to occur in a diffusionflame, while some of the non-catalytic combustion could occur in apremixed flame. The pre-heaters may also be configured for bothnon-catalytic combustion and catalytic combustion of the fuel stream.

Referring to FIG. 1A, fuel preheat mixture 119 may be partiallycatalytically combusted in fuel pre-heater 120 to provide heat toreforming fuel stream 124. Fuel pre-heater 120 may be any suitablecatalytic combustion chamber wherein the fuel in fuel preheat mixture119 is partially catalytically combusted, and may comprise a separatecatalytic reactor loaded with structured or unstructured catalyst or maycomprise a modified section of pipe that has been loaded with structuredor unstructured catalyst. In some embodiments, the fuel in fuel preheatmixture 119 is only partially catalytically combusted because the amountof air in the fuel preheat mixture 119 is deliberately insufficient tofully combust the fuel. In preferred embodiments, where the fuel preheatmixture 119 entering fuel pre-heater 120 is below metal dustingtemperatures and the reformer fuel stream 124 is above metal dustingtemperatures, metal dusting conditions may occur in fuel pre-heater 120,and therefore fuel pre-heater 120 is preferably constructed from metaldusting resistant metal or from metal coated with a metal dustingresistant coating and/or is configured for easy repair and/or removaland replacement.

Preferably fuel preheat mixture 119 is at a temperature below metaldusting conditions, such as at a temperature below 400° C., such asbelow 375° C., below 360° C., below 350° C., below 325° C. or below 300°C. Preferably the pressure of the fuel preheat mixture 119 is less than10 barg, such as less than 8 barg, less than 5 barg, less than 2.5 barg,less than 1 barg, less than 0.75 barg, less than 0.5 barg, less than 0.4barg, less than 0.3 barg, less than 0.2 barg, less than 0.15 barg, lessthan 0.10 barg or less than 0.075 barg. Preferably, the amount of air infuel preheat mixture 119 is just sufficient, when fully consumed inexcess fuel, to give the necessary reformer fuel temperature, with nofurther control of the reactor necessary.

Preferably reformer fuel stream 124 is at a temperature above metaldusting conditions, such as at a temperature above 775° C., above, 780°C., above 785° C., above 790° C., above 795° C., above 800° C., above805° C., above 810° C. or above 815° C. Preferably the pressure of thereformer fuel stream 124 is less than 10 barg, such as less than 8 barg,less than 5 barg, less than 2.5 barg, less than 1 barg, less than 0.75barg, less than 0.5 barg, less than 0.4 barg, less than 0.3 barg, lessthan 0.2 barg, less than 0.15 barg, less than 0.10 barg or less than0.075 barg, or less than 0.05 barg.

Air preheat mixture 117 may be combusted in air pre-heater 122 in thepresence of air feed stream 107 to form reforming air stream 126. Airpre-heater 122 may be any suitable catalytic combustion chamber whereinthe fuel in air preheat mixture 117 is catalytically combusted and maycomprise a separate catalytic reactor loaded with structured orunstructured catalyst or may comprise a modified section of pipe thathas been loaded with structured or unstructured catalyst. Unlike in fuelpre-heater 120, the fuel in air preheat mixture 117 is completely orsubstantially completely catalytically combusted because the amount ofair in the air pre-heater 122 is not limited to conserve fuel forfurther combustion downstream. In preferred embodiments, where the airpreheat mixture 117 entering fuel pre-heater 122 is below metal dustingtemperatures and the reformer air stream 126 is above metal dustingtemperatures, metal dusting conditions may occur in air pre-heater 122,and therefore air pre-heater 122 is preferably constructed from metaldusting resistant metal or from metal coated with a metal dustingresistant coating and/or is configured for easy repair and/or removaland replacement. By localizing the occurrence of metal dustingconditions or limiting the components within reformer system 100 thatare exposed to metal dusting conditions, the cost of the system and easeof use and repair/maintenance may be minimized.

In general, air preheat mixture 117 is at a temperature below metaldusting conditions, such as at a temperature below 400° C., such asbelow 375° C., below 360° C., below 350° C., blow 325° C. or below 300°C. Preferably the pressure of the air preheat mixture 122 is less than 1barg, such as less than 0.75 barg, less than 0.50 barg, less than 0.40barg, less than 0.30 barg, less than 0.20 barg, less than 0.15 barg,less than 0.10 barg, less than 0.075 barg, or less than 0.05 barg.Preferably, the amount of fuel in air preheat mixture 117 is justsufficient, when fully combusted in excess air, to give the necessaryreformer air temperature, with no further control of the reactornecessary.

Air feed stream 107 may enter air pre-heater 122 at essentially thetemperature and pressure it leaves syngas heat recovery heat exchanger110, such as at a temperature below metal dusting conditions and mayleave air pre-heater 122 as reformer air stream 126 at a temperatureabove metal dusting conditions, such as at a temperature above 800° C.,above 815° C., above 830° C., above 840° C., above 850° C., above 860°C., above 875° C., above 890° C., or above 900° C. Preferably thepressure of the reformer air stream 126 is less than less than 1 barg,such as less than 0.75 barg, less than 0.50 barg, less than 0.40 barg,less than 0.30 barg, less than 0.20 barg, less than 0.15 barg, less than0.10 barg, less than 0.075 barg, or less than 0.05 barg.

As shown in FIG. 1A, after leaving syngas heat recovery heat exchanger110, flue gas fuel stream 112 is combined with flue gas stream 160 fromthe reformer module 150 to form fuel-containing flue gas stream 162.Fuel-containing flue gas stream 162 is combusted in flue gas pre-heater175 via catalytic combustion of the fuel components in fuel-containingflue gas stream 162, forming heated flue gas stream 163. Alternatively,flue gas fuel stream 112 may feed directly to flue gas pre-heater 175,where it may mix with flue gas stream 160 and then be combusted to formheated flue gas stream 163. Heated flue gas stream 163 may provideadditional heat to water stream 108 in heat exchanger 164 after waterstream 108 leaves heat exchanger 109. From there heated flue gas stream163 may be exhausted as flue gas or may proceed to further downstreamprocessing.

Flue gas pre-heater 175 may be any suitable catalytic combustion chamberwherein the fuel in fuel-containing flue gas stream 162 (or in fuelstream 112, when fuel stream 112 connects directly to flue gaspre-heater 175) is catalytically combusted to provide heat to fuelcontaining flue gas stream 162 and may comprise a separate catalyticreactor loaded with structured or unstructured catalyst or may comprisea modified section of pipe that has been loaded with structured orunstructured catalyst. Preferably, fuel containing flue gas stream 162enters flue gas pre-heater 175 at a temperature between 200° C. and 450°C., such as between 225° C. and 440° C., between 250 and 425° C.,between 275° C. and 420° C., between 300 and 410° C., between 325 and400° C., or between 350 and 390° C. and a pressure less than 1 barg,such as less than 0.75 barg, less than 0.50 barg, less than 0.40 barg,less than 0.30 barg, less than 0.20 barg, less than 0.15 barg, less than0.10 barg, less than 0.075 barg, or less than 0.05 barg and leaves fluegas pre-heater 175 as heated flue gas stream 163 at a temperaturebetween 250° C. and 550° C., such as between 275° C. and 525° C.,between 300° C. and 500° C., between 350° C. and 490° C., between 375°C. and 475° C. or between 400° C. and 450° C., and at a pressure of lessthan 1 barg, such as less than 0.75 barg, less than 0.50 barg, less than0.40 barg, less than 0.30 barg, less than 0.20 barg, less than 0.15barg, less than 0.10 barg, less than 0.075 barg, or less than 0.05 barg.

Heat exchanger 164 may be any suitable heat exchanger for exchangingheat from heated flue gas stream 163 into water stream 108. In someembodiments, heat exchanger 164 may be a PCHE. In some embodiments, heatexchanger 164 may comprise a PCHE that is constructed from a series ofplates as shown in FIG. 3A-B. The plates may be combined into a stackand diffusion bonded or otherwise bonder to one another to form heatexchanger 164 to provide heat exchange between the entering hot and coldstreams. In general the flow paths for each of the streams may be formedin the plates by etching, milling or other suitable process and may beconfigured to provide for the desired heat exchange, while limitingpressure drop for one or more streams across the heat exchanger.Preferably, the streams entering and leaving exchanger 164 aremaintained at temperature, pressure and composition conditions thatavoid or reduce metal dusting conditions within the heat exchanger.

Referring to FIG. 3A-B, in some embodiments, heat exchanger 164 maycomprise one or more water feed plates 320 and one or more heated fluegas plates 350. Each of the plates may be constructed from materialssuitable for the purpose and the conditions present in exchanger 164.Examples of suitable materials for constructing plates 320 and 350include 316 stainless steel and 304 stainless steel. The water feedplates 320 and heated flue gas plates 350 may independently have thethicknesses described in Table 1. In some embodiments, the plates mayeach be 1.6 mm thick.

FIG. 3A shows heated flue gas flow plate 350 with heated flue gas streamflow path 351, which connects heated flue gas stream inlets 353 andheated flue gas stream outlets 356. Heated flue gas inlets 353 may splitthe heated flue gas stream 163 into multiple independent flow channels355 comprising heated flue gas stream flow path 351. Heated flue gasstream outlets 356 may re-combine the flow in flow channels 355 tore-form flue gas stream 163 as it leaves heat exchanger 164. Heated fluegas stream inlets 353 and heated flue gas stream outlets 356 connect toheated flue gas stream inlet penetration 358 and heated flue gas streamoutlet penetration 357 and heated flue gas flow plate 350 also includeswater inlet penetration 354 and water outlet penetration 352. Flowchannels 355 and adjacent ridges may be sized to provide for safepressure containment and a cost effective combination of heat transfercapacity and pressure drop. In some embodiments, independent flowchannels 355 may each comprise a generally semicircular cross-sectionand may have the dimensions described in Table 1. In some embodiments,independent flow channels 355 may each have a semicircular cross-sectionwith a width of about 1.9 mm, a depth of about 1.0 mm and about 0.4 mmridges. Though a specific number of independent flow channels 355 areshown, it should be understood that water stream flow path 351 maycomprise any suitable number of independent flow channels configuredappropriately according to the individual needs of the system.

Though FIG. 3A shows heated flue gas stream flow path 351 as a directcross flow or single pass flow path, in some embodiments heated flue gasstream flow path 351 may comprise more than one pass, each passcomprising a single reversal in flow direction, such as from 2 to 20passes, 2 to 10 passes or 2 to 5 passes. Preferably, heated flue gasstream flow path 351 comprises a direct cross flow or single pass flowpath during heat exchange and flows in a counter flow direction relativeto the general flow of the water stream.

FIG. 3B shows water feed plate 320 having a water stream flow path 321which connects water stream inlets 326 and water stream outlets 323.Water stream flow path 321 may comprise one or multiple independent flowchannels 325. Water stream inlets 326 and water stream outlets 323connect to water inlet penetration 324 and water outlet penetration 322,respectively, and water feed plate 320 also includes heated flue gasstream outlet penetration 327 and heated flue gas stream inletpenetration 328. Flow channels 325 and adjacent ridges may be sized toprovide for safe pressure containment and a cost effective combinationof heat transfer capacity and pressure drop. In some embodiments,independent flow channels 325 may each comprise a generally semicircularcross-section and may have the dimensions described in Table 1. In someembodiments, independent flow channels 325 may each have a semicircularcross-section with a width of about 1.63 mm, a depth of about 0.75 mmand about 0.4 mm ridges. Though a specific number of independent flowchannels 325 are shown, it should be understood that water stream flowpath 321 may comprise any suitable number of independent flow channelsconfigured appropriately according to the individual needs of thesystem.

Though FIG. 3B shows water stream flow path 321 as a multi-pass singlechannel flow path, flow path 321 may also comprise a direct counterflow, co-flow, cross flow or single pass flow path comprising multipleindependent channels. In some embodiments water stream flow path 321 maycomprise more than one pass, each pass comprising a single reversal inflow direction, such as from 2 to 100 passes, 5 to 75 passes, 10 to 60passes, 15 to 50 passes or 20 to 40 passes. Preferably, water streamflow path 321 comprises a multi-pass flow path having 5 passes orgreater, 10 passes or greater, 15 passes or greater, 20 passes orgreater, 25 passes or greater or 30 passes or greater where the passesare in cross flow during heat exchange, and where the water stream flowsin a generally counter-flow direction relative to the heated flue gasstream.

In some embodiments, the plates used to form embodiments of heatexchanger 164 may be stacked and diffusion bonded or otherwise bonded inany suitable order to form heat exchanger 164. In some embodiments, theplates may be stacked and diffusion bonded or otherwise bonded in orderas follows: at least one 1 end plate (not shown), multiple heat exchangecells, each heat exchange cell comprising a heated flue gas flow plate350 followed by a water stream feed plate 320, followed by a finalheated flue gas flow plate 350, and then at least 1 end plate (notshown). Accordingly, the order of the printed circuit heat exchangeplates in a given stack for heat exchanger 164 may have the followingpattern (Endplate=“E”, Flue gas plate 350=“F”, water stream feed plate320=“W”): E F W F F W F F W F . . . F W F F W F E). The end plates maybe blank plates with no flow path circuitry and may be insulated toenhance heat transfer and limit heat loss. The end plates may serve aslids to the penetrations and support connection of the relevant streamsto heat exchanger 164, such as via ports or headers. Accordingly, theendplates should be thick enough to accommodate the pressures in each ofthe penetrations and to support the ports or headers. In someembodiments, a single endplate is used for each end of the exchanger164, where the endplate is thicker than the other plates. In otherembodiments, multiple endplates may be used at each end to providesufficient thickness to support or provide for the headers or ports. Insome embodiments, heat exchanger 164 may comprise a stack that isbetween 50 mm and 70 mm tall, such as 60 mm tall.

In some embodiments, heat exchanger 164 comprises from 2 to 30 heatexchange cells, such as from 5-25, from 7-20, from 8 to 17 or from 10 to15 heat exchange cells, each heat exchange cell comprising a heated fluegas flow plate 350 followed by a water stream feed plate 320, followedby a heated flue gas flow plate 350. In preferred embodiments forreforming 2 SCMH of natural gas using PSA off-gas as fuel, heatexchanger 164 comprises at least 10 heat exchange cells. In onepreferred embodiment, heat exchanger 164 comprises 10 heat exchangecells, each heat exchange cell comprising a heated flue gas flow plate350 followed by a water stream feed plate 320, and comprises anadditional heated flue gas flow plate 350, and six endplates for a totalof 30 active plates. The number of plates and heat exchange cells may bemodified according to production needs, heat exchange efficiency andother parameters.

When the various plates are stacked and diffusion bonded or otherwisebonded to form a heat exchanger, heated flue gas stream inletpenetrations 358 and heated flue gas stream outlet penetrations 357 arepreferably aligned with heated flue gas stream inlet penetrations 328and heated flue gas stream outlet penetrations 327 on the water feedplates 320 to form inlet and outlet flow access paths or chambers forthe heated flue gas stream. In addition, the water stream inletpenetrations 324 and 356 and the water stream outlet penetrations 322and 355 are also preferably aligned to form inlet and outlet flow accesspaths or chambers for the water stream. The stacking of the plates alsopreferably places flow paths 321 and 351 in close proximity to oneanother to facilitate heat transfer between the streams through thewalls of independent channels 325 and 355.

In some embodiments, water stream 108 may enter heat exchanger 164 atessentially the temperature and pressure that it leaves syngas heatrecovery heat exchanger 110 and may leave exchanger 164 at a temperatureof between 120° C. and 210° C., such as between 130° C. and 205° C.,between 150° C. and 200° C. or between 175° C. and 195° C. and at apressure between 10 bara and 100 bara, such as between 10 bara and 90bara, between 10 bara and 75 bara, between 10 bara and 60 bara, between10 bara and 50 bara, between 10 bara and 40 bara, between 10 bara and 30bara, between 10 bara and 20 bara, between 10 bara and 18 bara, between11 bara and 17 bara, between 12 bara and 16 bara, between 13 bara and 15bara or between 13.5 bara and 14.5 bara. Preferably, the pressure dropfor water stream 108 across heat exchanger 164 is less than 1 bar, suchas less than 0.75 bar, less than 0.60 bar less than 0.50 bar, less than0.40 bar or less than 0.30 bar.

Heated flue gas stream 163 may enter heat exchanger 164 at essentiallythe temperature and pressure that it left flue gas pre-heater 175 andmay leave exchanger 164 at a temperature of between 120° C. and 200° C.,such as between 125° C. and 180° C., between 130° C. and 160° C. orbetween 140° C. and 150° C. and a pressure of less than 0.02 barg, suchas less than 0.015 barg, or less than 0.010 barg.

After leaving heat exchanger 164, water stream 108 may enter quench heatexchanger 165 where it may be further heated to raise steam for thereforming process. Quench heat exchanger 165 may comprise heat exchanger166 submerged in water in a tank or vessel. Quench heat exchanger 165may be used to quench syngas quench stream 170. Syngas quench stream 170may be a portion of syngas stream 180 leaving reformer module 150.Syngas stream 180 may be split using syngas stream splitter 184 to formsyngas quench stream 170 and syngas stream 182. Syngas stream splitter184 may be any suitable means of splitting the flow of syngas stream180, such as a “T” or “Y” piping connection and may direct the desiredamount of flow in each direction to ensure adequate steam production inquench heat exchanger 165 and adequate hydrogen production in optionalwater-gas shift reactor 186 or adequate syngas temperature and pressureentering syngas heat recovery heat exchanger 110. Preferably, quenchheat exchanger 165 and heat exchanger 166 are configured such that theflow of syngas quench stream 170 remains turbulent throughout thedesired turndown range in which system 100 is operated.

As long as heat exchanger 166 remains submerged in the water in quenchexchanger 165, metal dusting conditions are avoided in the exchangerbecause the temperature of the exchanger never rises above the boilingpoint of the water, as the temperature of the water remains essentiallyconstant during the phase transition. Though avoided in the quench heatexchanger 165, metal dusting conditions may occur in syngas quenchstream 170 adjacent to quench heat exchanger 165, and therefore aportion of syngas quench stream 170 is preferably constructed from metaldusting resistant metal or metal coated with a metal dusting resistantcoating and/or is configured for easy repair and/or removal andreplacement. Ideally, the portion of syngas quench stream 170 that isexposed to metal dusting conditions is minimized and is configured tominimize repair, maintenance and replacement. In some embodiments, themetal dusting conditions within stream 170 are preferably limited towithin 5 pipe diameters of the entrance to quench heat exchanger 165 andtherefore the piping in this portion of the system may be constructedfrom metal dusting resistant metal or metal coated with a metal dustingresistant coating and/or is configured for easy repair and/or removaland replacement. In this fashion, steam may be raised from the hotsyngas to be used for the reforming stages, while metal dustingconditions are localized in a small portion of the syngas quench stream170. Quench heat exchanger 165 also comprises steam outlet 167 and waterblow down 168. Steam formed in quench heat exchanger 165 may passthrough steam outlet 167 and proceed further into the system 100. Wastewater and dissolved solids may be periodically blown down through waterblow down 168 by actuation of valve 169 to prevent or limit build-up inquench heat exchanger 165.

Heat exchanger 166 may be partially or completely submerged in waterfrom water stream 108 after it leaves heat exchanger 164. Heat exchanger166 and the heat it transfers from the syngas quench stream 170 to thewater preferably generate the bulk of the steam used in the reformermodule 150. In some embodiments, heat exchanger 166 may be a PCHE. Insome embodiments, heat exchanger 166 may comprise a PCHE that isconstructed from a series of plates as shown in FIG. 4A-D. The platesmay be combined into a stack and diffusion bonded or otherwise bonder toone another to form heat exchanger 166 to provide heat exchange betweenthe entering hot and cold streams. In general the flow paths for each ofthe streams may be formed in the plates by etching, milling or othersuitable process and may be configured to provide for the desired heatexchange, while limiting pressure drop for one or more streams acrossthe heat exchanger. Preferably, the streams entering and leavingexchanger 166 are maintained at temperature, pressure and compositionconditions that avoid or reduce metal dusting conditions within the heatexchanger.

Referring to FIG. 4A-D, in some embodiments, heat exchanger 166 maycomprise one or more water plates 410, one or more syngas quench streamplates 420, one or more top endplates 430 and one or more bottomendplates 440. Each of the plates may be constructed from materialssuitable for the purpose and the conditions present in exchanger 166.Examples of suitable materials for constructing plates 320 and 350include 316 stainless steel and 304 stainless steel. The plates mayindependently have the thicknesses described in Table 1. In someembodiments, the plates may each be 1.6 mm thick.

FIG. 4A shows water plate 410 having a water stream flow path 411 whichconnects water stream inlets 412 and water stream outlets 413. Waterstream inlets 412 may split the water flow into one or multipleindependent flow channels 414 that form flow path 411. Water streamoutlets 413 may re-combine flow channels 414 for exit from heatexchanger 166. Flow channels 414 may be configured for thermosyphonboiling of the water within exchanger 166 and may be formed in anysuitable shape and size. In some embodiments, independent flow channels414 may each comprise a generally semicircular cross-section and mayhave the dimensions described in Table 1. In some embodiments,independent flow channels 414 may each have a semicircular cross-sectionwith a width of about 2.6 mm, a depth of about 1.10 mm and 0.4 mmridges. Though a specific number of independent flow channels 414 areshown, it should be understood that water stream flow path 411 maycomprise any suitable number of independent flow channels configuredappropriately according to the individual needs of the system.

In some embodiments, water stream inlets 412 and outlets 413 may alsocomprise a generally semicircular cross-section having a width of from0.6 mm to 3.5 mm, a depth of from 0.3 to 1.75 mm and ridges of from 0.3mm to 1.5 mm and may be sized the same or differently than independentflow channels 414. In some embodiments, inlets 412 and outlets 413 eachhave a semicircular cross-section with a width of about 2.6 mm, a depthof about 1.10 mm and 0.4 mm ridges. Though FIG. 4A shows water streamflow path 411 as a direct counter or co-flow or single pass flow path,in some embodiments water stream flow path 411 may comprise more thanone pass, each pass comprising a single reversal in flow direction, suchas from 2 to 20 passes, 2 to 10 passes or 2 to 5 passes. Preferably,water stream flow path 411 comprises a direct or single pass co-flowflow path. As shown in FIG. 4A, water stream plate 410 also includessyngas quench stream inlet and outlet penetrations 415 and 416respectively.

Referring to FIG. 4B, syngas quench stream plates 420 may have a syngasquench stream flow path 421, which connects syngas quench stream inletpenetrations 422 and syngas quench stream outlet penetrations 423.Syngas quench stream inlet penetrations 422 may feed inlet channels 426,which may be further split to form one or multiple independent flowchannels 424 that make up flow path 421. Syngas quench stream outlet 423may recombine multiple outlet channels 425 which may recombineindependent flow channels 424 for exit from the heat exchanger. Inletand outlet channels 426 and 425 and independent flow channels 424 mayeach comprise a generally semicircular cross-section and may have thedimensions described in Table 1. In some embodiments, independent flowchannels 424 may each have a semicircular cross-section with a width ofabout 1.99 mm, a depth of about 1.10 mm and 0.4 mm ridges. In someembodiments, inlet and outlet channels 426 and 425 may each have asemicircular cross-section with a width of about 2.2 mm, a depth ofabout 1.10 mm and 0.4 mm ridges. Though a specific number of independentflow channels 414 are shown, it should be understood that water streamflow path 411 may comprise any suitable number of independent flowchannels configured appropriately according to the individual needs ofthe system.

Though FIG. 4B shows syngas quench stream flow path 421 as a directcounter or co-flow or single pass flow path, in some embodiments syngasquench stream flow path 421 may comprise more than one pass, each passcomprising a single reversal in flow direction, such as from 2 to 20passes, 2 to 10 passes or 2 to 5 passes. Preferably, syngas quenchstream flow path 421 comprises a direct or single pass co-flow flowpath.

In some embodiments, the plates used to form embodiments of heatexchanger 166 may be stacked and diffusion bonded or otherwise bonded inany suitable order to form the heat exchanger. In some embodiments theplates may be stacked and diffusion bonded or otherwise bonded in orderas follows: at least one top end plate 430 (FIG. 4C), multiple heatexchange cells, each heat exchange cell comprising a water plate 410followed by a syngas quench stream flow plate 420, with one additionalwater plate and then at least one bottom end plate 440 (FIG. 4D).Accordingly, the order of printed circuit heat exchange plates in agiven stack for heat exchanger 166 may have the following pattern forthe active plates of heat exchanger 166, (water plate 410=W; syngasquench stream plate 420=S): W S W S W S . . . W S W S W. In someembodiments, the configuration will comprise cells of alternating waterplates 410 and syngas quench stream plates 420 with one extra waterplate 410 to serve as a bounding plate for the last syngas quench streamplate 420 in the stack. The end plates may be blank plates with no flowpath circuitry and may be insulated to enhance heat transfer and limitheat loss. In some embodiments, multiple endplates may be used at eachend. The end plates provide a wall for the passages on the boundingplate facing the end plate, serve as lids to the penetrations andsupport connection of the relevant streams to heat exchanger 166, suchas via ports or headers. Accordingly, the endplates should be thickenough to accommodate the pressures in each of the penetrations and tosupport the ports or headers. In some embodiments, a single endplate isused for each end of the exchanger 166, where the endplate is thickerthan the other plates. In other embodiments, multiple endplates may beused at each end to provide sufficient thickness to support or providefor the headers or ports. In some embodiments, heat exchanger 166 maycomprise a stack that is between 15 and 25 mm tall.

In some embodiments, top end plate 430 may include a syngas stream inletpenetration 432 and a syngas stream outlet penetration 431 for entry andexit of the syngas quench stream. When the various plates are stackedand diffusion bonded or otherwise bonded to form a heat exchanger,syngas stream inlet penetrations 432 and syngas stream outletpenetrations 431 are preferably aligned with syngas quench stream inletpenetrations 422 and syngas quench stream outlet penetrations 423 on thesyngas quench stream plates 420 and with the syngas quench stream inletand outlet penetrations 414 and 415 on water plates 410 to form inletand outlet flow access paths or chambers for the syngas quench stream.The stacking of the plates also preferably places flow paths 411 and 421in close proximity to one another to facilitate heat transfer betweenthe streams through the walls of independent channels 414 and 424. Forthose plates and streams that do not have penetrations through which theflow paths and flow channels are accessed, headers may be attached, suchas welded, over the individual channel ends to facilitate deliveryand/or collection of the stream flowing through the relevant channels.

In some embodiments, heat exchanger 166 comprises from 1 to 15 heatexchange cells, such as from 2 to 10, from 3 to 8, from 4 to 7 or from 5to 7 heat exchange cells, each heat exchange cell comprising a waterplate 410 followed by a syngas quench stream flow plate 420. Inpreferred embodiments for reforming approximately 2 SCMH of natural gasusing PSA off-gas or tail gas as fuel, heat exchanger 166 comprises atleast 4 heat exchange cells. In one preferred embodiment, heat exchanger166 comprises 4 heat exchange cells, each heat exchange cell comprisinga water plate 410 followed by a syngas quench stream flow plate 420, and4 endplates for a total of 9 active plates. The number of plates andheat exchange cells may be modified according to production needs, heatexchange efficiency and other parameters.

Water stream 108 may enter quench heat exchanger 165 at essentially thetemperature and pressure it left heat exchanger 164 and may leaveexchanger 165 as reformer steam supply 172 at a temperature equal to thesaturated steam temperature, such as between 175° C. and 225° C.,between 180° C. and 210° C., between 185° C. and 205° C., between 190and 205° C. or between 195 and 200° C. and at a pressure of between 10bara and 100 bara, such as between 10 bara and 90 bara, between 10 baraand 75 bara, between 10 bara and 60 bara, between 10 bara and 50 bara,between 10 bara and 40 bara, between 10 bara and 30 bara, between 10bara and 20 bara, between 10 bara and 18 bara, between 11 bara and 17bara, between 12 bara and 16 bara, between 13 bara and 15 bara orbetween 13.5 bara and 14.5 bara.

Syngas quench stream 170 may enter quench heat exchanger 165 at atemperature of between 700° C. and 1000° C., such as between 750° C. and975° C. or between 800° C. and 950° C., between 825° C. and 925° C. orbetween 850° C. and 900° C. and at a pressure of between 5 bara and 120bara, such as between 10 bara and 100 bara, between 10 bara and 80 bara,between 10 bara and 60 bara, between 10 bara and 50 bara, between 10bara and 40 bara, between 10 bara and 30 bara, between 10 bara and 20bara, between 10 bara and 18 bara, between 11 bara and 17 bara, between12 bara and 16 bara, between 13 bara and 15 bara or between 13.5 baraand 14.5 bara and may leave exchanger 165 at a temperature of between180° C. and 210° C., such as between 185° C. and 205° C., between 190and 205° C. or between 195 and 200° C. and at a pressure of between 5bara and 120 bara, such as between 10 bara and 100 bara, between 10 baraand 80 bara, between 10 bara and 60 bara, between 10 bara and 50 bara,between 10 bara and 40 bara, between 10 bara and 30 bara, between 10bara and 20 bara, between 10 bara and 18 bara, between 11 bara and 17bara, between 12 bara and 16 bara, between 13 bara and 15 bara orbetween 13.5 bara and 14.5 bara. Preferably, the pressure drop forsyngas quench stream 170 across exchanger 165 is less than 0.10 bar,such as less than 0.075 bar or less than 0.05 bar.

Water stream 108 is heated in quench heat exchanger 165 until it becomessteam at which point the steam leaves quench heat exchanger 165 throughsteam outlet 167 as reforming steam supply 172. Reforming steam supply172 may be combined with gaseous hydrocarbon stream 102 after stream 102leaves syngas heat recovery heat exchanger 110 to formgaseous/hydrocarbon steam stream 174. Reforming steam supply 172 andgaseous hydrocarbon stream 102 may be joined in any suitable manner,such as by joining the streams to form a single stream using a “Y” or“T” connector or by adding one stream into the other stream. Aftercombining the streams, gaseous hydrocarbon-steam stream 174 may be fedto the first pre-reforming stage of reformer module 150. In someembodiments, the reforming steam supply 172 may include a back pressureregulator within its flow path prior to joining gaseous hydrocarbonstream 102 to help provide for stable boiling conditions duringstart-up, capacity changes and other transients, thereby avoiding surgesof liquid water into the reformer module or starvation of steam flow tothe reformer which could lead to coking in the reformer and/orpre-reformer. In some embodiments, gaseous hydrocarbon steam stream mayalso include a check valve within its flow path prior to being joinedwith reforming steam supply 172.

After being quenched in quench heat exchanger 165, syngas quench stream170 may leave quench exchanger 165 as quenched syngas stream 171 andpass through valve 185, which may be any suitable valve for controllingor tuning the supply of quenched syngas 171 to syngas re-mixer 188.After proceeding through valve 185, quenched syngas stream 171 may bejoined with syngas stream 182 in syngas re-mixer 188. Syngas stream 182proceeds from syngas splitter 184 through fixed resistor 187, which maybe a simple orifice or any other method of controlling high temperatureflows. Generally, syngas stream 182 is too hot to employ a valve.Preferably, syngas stream 182 is at a temperature of between 700° C. and1000° C., such as between 750° C. and 975° C. or between 800° C. and950° C., between 825° C. and 925° C. or between 850° C. and 900° C. andat a pressure of between 5 bara and 120 bara, such as between 10 baraand 100 bara, between 10 bara and 80 bara, between 10 bara and 60 bara,between 10 bara and 50 bara, between 10 bara and 40 bara, between 10bara and 30 bara, between 10 bara and 20 bara, between 10 bara and 18bara, between 11 bara and 17 bara, between 12 bara and 16 bara, between13 bara and 15 bara or between 13.5 bara and 14.5 bara.

Syngas re-mixer 188 may be any suitable apparatus for joining twostreams, such as by joining the streams to form a single stream using a“Y” or “T” connector or by adding one stream into the other stream.Because of the temperature in syngas stream 182 relative to thetemperature in quenched syngas stream 171, a portion of remixed syngasstream 189 and a portion of syngas stream 182 may be exposed to metaldusting conditions. Accordingly, a portion of syngas stream 182 withinabout 5 pipe diameters of re-mixer 188 and a portion of re-mixed syngasstream 189 within about 5 pipe diameters of re-mixer 188 are preferablyconstructed from metal dusting resistant alloys and/or alloys having ametal dusting resistant coating and/or is configured for easy repairand/or removal and replacement.

After being re-mixed, re-mixed syngas stream 189 may proceed to anoptional water-gas shift reactor 186, where additional hydrogen israised via the water-gas shift reaction. When a water-gas shift reactoris used, the temperature of re-mixed syngas stream 189 is preferablybetween 250° C. and 350° C., such as between 275° C. and 325° C.,between 280° C. and 310° C., between 290° C. and 305° C. or between 295°C. and 300° C.

After leaving the water-gas shift reactor 186, syngas stream 190 mayproceed to syngas heat recovery heat exchanger 110 where it may provideheat for the reactant feed streams, such as gaseous hydrocarbon stream102, flue gas fuel stream 112, fuel feed stream 105, air feed stream107, combustion air stream 114, and water stream 108 (when heatexchanger 109 is part of syngas heat recovery heat exchanger 110).Syngas stream 190 leaving the high temperature shift reactor may have atemperature between 250° C. and 450° C., such as between 275° C. and450° C., between 300° C. and 440° C., between 325° C. and 430° C.,between 350° C. and 420° C., between 375° C. and 410° C. or between 380°C. and 400° C. and a pressure between 10 bara and 100 bara, between 10bara and 80 bara, between 10 bara and 60 bara, between 10 bara and 50bara, between 10 bara and 40 bara, between 10 bara and 30 bara, between10 bara and 20 bara, between 10 bara and 18 bara, between 11 bara and 17bara, between 12 bara and 16 bara, between 13 bara and 15 bara orbetween 13.5 bara and 14.5 bara.

An example of an alternative configuration for the steam reformingapparatus is shown in FIG. 5. As shown, steam reforming apparatus 500 issubstantially the same as apparatus 100 described with respect to FIG.1A and/or FIG. 1B, with the exception that in steam reforming apparatus500, flue gas fuel stream 512 bypasses the syngas heat exchanger 510 andis combined with flue gas stream 160 just prior to entering flue gaspre-heater 175 to form fuel rich flue gas stream 162. Flue gas fuelstream 512 may be combined with flue gas stream 160 in any suitablemanner such as by joining the streams to form a single stream using a“Y” or “T” connector or by adding one stream into the other stream.Because flue gas fuel stream 512 bypasses syngas heat exchanger 510,syngas heat recovery heat exchanger 510, is configured slightlydifferently, having only 4 reactant feed streams (fuel feed stream 105,air feed stream 107, combustion air stream 114 and gaseous hydrocarbonfeed stream 102), optionally water feed stream 108 (when heat exchanger109 is included in heat exchanger 510) and syngas stream 190 flowingthrough it.

An example configuration of plates that may form syngas heat recoveryheat exchanger 510 is shown in FIG. 6A-C. Referring to FIG. 6A-C, insome embodiments syngas heat recovery heat exchanger 510 may comprise aPCHE that is constructed from a series of plates that may be combinedinto a stack and diffusion bonded to one another to provide heatexchange between the entering hot and cold streams. In general the flowpaths for each of the streams may be formed in the plates by etching,milling or other suitable process and may be configured to provide forthe desired heat exchange, while limiting pressure drop for one or morestreams across the heat exchanger. Preferably, the streams entering andleaving exchanger 510 are maintained at temperature, pressure andcomposition conditions that avoid or reduce metal dusting conditionswithin the heat exchanger. In most instances, the streams entering andleaving heat exchanger 510 are below metal dusting temperatures. Ingeneral, syngas heat recovery heat exchanger 510 is essentially the sameas syngas heat recovery heat exchanger 110 shown in FIGS. 1 and 2A-C,with the exception that syngas heat recovery heat exchanger 510 does notheat the flue gas fuel stream 512. Accordingly, with this minorexception, the general construction of syngas heat recovery heatexchanger 510, the suitable plate and channel dimensions, thicknesses,and materials of construction for each of the plates and processconditions are substantially the same as those described with respect toFIG. 2A-C.

Referring to FIG. 6A-C, in some embodiments, syngas heat recovery heatexchanger 510 may comprise one or more bounding plates 610, one or morereactant feed plates 625 and one or more syngas plates 650. In theembodiment shown in FIG. 6A-C, the plates, when appropriately stackedand formed into a heat exchanger, will form a syngas heat recovery heatexchanger 510 that includes heat exchanger 109 (See FIG. 5). FIG. 6Ashows a bounding plate 610 having a syngas flow path 611 comprisingindependent flow channels 612 connecting syngas inlets 613 with syngasoutlets 614. Though FIG. 6A shows syngas flow path 611 as a multi-passflow path, flow path 611 may also comprise a direct counter flow,co-flow, cross flow or single pass flow path comprising one or multipleindependent channels 612. In some embodiments syngas flow path 611 maycomprise more than one pass, each pass comprising a single reversal inflow direction, such as from 2 to 100 passes, 5 to 75 passes, 10 to 60passes, 15 to 50 passes or 20 to 40 passes. Preferably, syngas flow path611 comprises a multi-pass flow path having 5 passes or greater, 10passes or greater, 15 passes or greater, 20 passes or greater, 25 passesor greater or 30 passes or greater where the passes are in cross flowduring heat exchange, but the syngas flows in a generally cross flow orcounter-flow direction relative to the flows on the reactant feed plate260. Bounding plate 610 also includes air stream penetrations 615,combustion air stream penetration 616, fuel stream penetration 617,fuel/air mixture penetration 661, gaseous hydrocarbon streampenetrations 618, water stream penetrations 619 and syngas streampenetrations 620. Bounding plate 610 ensures that all of the reactantfeed plates 625 have hot stream plates on both sides either a boundingplate 610 or a syngas plate 650 and helps serve to balance the heatloads and the heat flux throughout the stacks. Bounding plate 610 mayhave more than one flow channels 612.

Referring to FIG. 6B, syngas plate 650 includes syngas inlets 651,syngas outlets 652 and syngas flow path 653. Syngas flow path 653 maycomprise one or multiple syngas independent flow channels 654. Though aspecific number of syngas independent flow channels 654 are shown, itshould be understood that syngas flow path 653 may comprise any suitablenumber of independent flow channels configured appropriately accordingto the individual needs of the system.

Though FIG. 6B shows syngas flow path 653 having a specific number ofpasses, in some embodiments syngas flow path 653 may comprise more thanone pass, each pass comprising a single reversal in flow direction, suchas from 2 to 100 passes, 5 to 75 passes, 10 to 60 passes, 15 to 50passes or 20 to 40 passes. Preferably, syngas flow path 653 comprises amulti-pass flow path having 5 passes or greater, 10 passes or greater,15 passes or greater, 20 passes or greater, 25 passes or greater or 30passes or greater where the passes are in cross flow during heatexchange, but the syngas flows in a generally cross flow or counter-flowdirection relative to the flows on the reactant feed plate 525. Syngasplate 650 also has air stream penetrations 655, combustion air streampenetration 656, fuel stream penetration 657, fuel/air mixturepenetration 663, gaseous hydrocarbon stream penetrations 658, waterstream penetrations 659 and syngas stream penetrations 660.

Referring to FIG. 6C, reactant feed plate 625 has air streampenetrations 621, combustion air stream penetration 622, fuel streampenetration 623, fuel/air mixture penetration 662, gaseous hydrocarbonstream penetrations 624, water stream penetrations 626 and syngas streampenetrations 646. Reactant feed plate 625 includes air flow path 627with air inlets 628 and air outlets 629, combustion air flow path 630with combustion air inlets 631, fuel flow path 632 with fuel inlets 633and fuel/air mixture outlets 634 and gaseous hydrocarbon flow path 635with gaseous hydrocarbon inlets 636 and gaseous hydrocarbon outlets 637.Each of flow paths 627, 630, 632 and 635 may comprise one or multipleindependent flow channels 638, 639, 640 and 641 respectively. Ingeneral, each of independent flow channels 638, 639, 640 and 641 andadjacent ridges may be sized to provide for safe pressure containmentand a cost effective combination of heat transfer capacity and pressuredrop. Though a specific number of independent flow channels 638, 639,640 and 641 are shown in FIG. 6, it should be understood each of flowpaths 627, 630, 632 and 635 may comprise any suitable number ofindependent flow channels configured appropriately according to theindividual needs of the system.

Though FIG. 6C shows each of flow paths 627, 630, 632 and 635 as beingcross flow and/or single pass, in some embodiments one or more of flowpaths 627, 630, 632 and 635 may comprise multiple passes, such as from 2to 20 passes, from 2 to 10 passes or from 2 to 5 passes. Preferably,flow paths 627, 630, 632 and 635 are cross flow and/or single pass flowpaths. In FIG. 6C, combustion air flow path 630 is configured to providefor mixing the combustion air stream 114 of FIG. 5, with fuel feedstream 105 inside exchanger 510 by directing air flowing through flowpath 630 and fuel flowing in flow path 632 to the same penetration,fuel/air mixture penetration 662. When configured in this manner, thereis no separate joining of these streams downstream of syngas heatrecovery heat exchanger 510 as is depicted in FIG. 5.

Reactant feed plate 625 also includes a water stream flow path 642 whichconnects water stream inlets 643 and water stream outlets 644 as shownin the lower left portion of the reactant feed plate 625 in FIG. 6C.Water stream flow path 642 may comprise one or multiple independent flowchannels 645. This portion of reactant feed plate 625, when formed intoa heat exchanger corresponds to the water flow streams for heatexchanger 109 as indicated in FIG. 5. Flow channels 645 may be sized toprovide appropriate water supply at the desired pressure and temperatureto the rest of the reformer system 500. Though one independent flowchannel 645 is shown in FIG. 6C, it should be understood that flow path642 may comprise any suitable number of independent flow channelsconfigured appropriately according to the individual needs of thesystem.

Though FIG. 6C shows flow path 642 configured as a multi-loop ormulti-pass counter-flow flow path, it may also be cross flow, co-flow,and/or single pass. In some embodiments flow path 642 may comprise morethan one pass, each pass comprising a single reversal in flow direction,such as from 2 to 100 passes, 5 to 75 passes, 10 to 60 passes, 15 to 50passes or 20 to 40 passes. Preferably, water stream flow path 642comprises a multi-pass flow path having 5 passes or greater, 10 passesor greater, 15 passes or greater, 20 passes or greater, 25 passes orgreater or 30 passes or greater where the passes are in cross flowduring heat exchange, but the water flows in a generally cross flow orcounter-flow direction relative to the flow of the syngas on syngasplate 650.

When stacked and diffusion bonded or otherwise bonded to form a heatexchanger, the various bounding plates 610, reactant feed plates 625 andsyngas plates 650 are preferably aligned such that each of the variousair stream penetrations 615, 621 and 655, combustion air streampenetrations 616, 622 and 656, fuel stream penetrations 617, 623 and657, fuel/air mixture penetrations 661, 662 and 663, gaseous hydrocarbonstream penetrations 618, 624 and 658, water stream penetrations 619, 626and 659 and syngas stream penetrations 620, 627 and 660 form flow accesspaths or chambers for connection of each of the various streams to theappropriate inlets and outlets for the various flow paths. The platesmay be stacked in order as described with respect to FIG. 2 and maycomprise the same number of cells and configuration as described withrespect to FIG. 2. In addition to aligning the various penetrations, thestacking of the plates preferably places the independent channels 638,639, 640 and 641 making up flow paths 627, 630, 632 and 635 in closeproximity to the independent channels 612 and 654 making up flow paths611 and 653 to facilitate heat transfer between the relevant streamsthrough the walls of the respective independent channels.

An example of another alternative configuration for the steam reformingapparatus is shown in FIG. 7. As shown, steam reforming apparatus 700 issubstantially the same as apparatus 100 described with respect to FIG.1A and/or FIG. 1B, with the exceptions that in steam reforming apparatus700, the flue gas stream 160 is not pre-heated prior to entering heatexchanger 164. Accordingly, relative to FIG. 1A, fuel feed stream 104 isnot split, there is no flue gas fuel stream 114 and flue gas pre-heater175 has also been removed. As a result, syngas heat recovery heatexchanger 710 may be configured as discussed above with respect to FIG.6A-C. The configuration in FIG. 7 is intended for situations where thereformer is operated at elevated temperatures relative to the system ofFIG. 1A. In such situations, syngas stream 180 and flue gas stream 160leave the reforming stages at temperatures approaching 1000° C. At thishigher temperature, the additional steam raised with the assistance ofcombustion chamber 175 of FIG. 1A or 5 is not required, as reforming ata higher temperature provides higher methane conversion, for a givensteam-to-carbon ratio and the additional heat recovered from the syngasstream 180 and the flue gas stream 160 is sufficient to raise thenecessary steam for reforming at the elevated temperature.

Referring to FIGS. 1A, 5 and 7, each of reforming apparatuses 100, 500and 700 include a reformer module 150. Reformer module 150 reformsgaseous hydrocarbon-steam stream 174 to form syngas stream 180 and fluegas stream 160. During the reforming process, reforming fuel stream 124is combusted in the presence of reforming air stream 126 to provideadditional heat to the reforming process. An example of an embodiment ofa reformer module 150 is shown in FIG. 8. As shown in FIG. 8, in someembodiments reformer module 150 may comprise a pre-reformer 800 and areformer 820. Pre-reformer 800 may comprise multiple stages 801, 802 and803 of heat exchange between the gaseous hydrocarbon-steam stream 174and the flue gas stream 160 in heat exchangers 804, 805 and 806 followedby partial catalytic reforming of the gaseous hydrocarbon-steam stream174 in catalytic reforming chambers or beds 807, 808 and 809. Though theembodiment in FIG. 8 shows three pre-reforming stages 801-803, thenumber of pre-reforming stages may be varied from 1 to 10 depending onthe requirements of the system. Preferably, metal dusting and cokingconditions are avoided throughout the pre-reforming stages. Inoperation, pre-reformer 800 includes multiple iterations or stages ofheating gaseous hydrocarbon-steam stream 174 by recovering heat fromflue gas stream 160 followed by partial catalytic reforming of theheated gaseous hydrocarbon-steam stream.

In some embodiments, pre-reformer 800 comprise a PCR that is constructedfrom a series of plates as shown in FIG. 9A-E that have been stacked anddiffusion bonded or otherwise bonded to form a PCR. Such a PCR may beconfigured similar to a PCHE, with catalyst chambers or beds providedintermittently within the flow path of the gaseous hydrocarbon-steamstream 174 such that the stream may be alternately heated by flue gasstream 160 and then partially reformed catalytically. The PCR may beconstructed from a series of plates that may be combined into a stackand diffusion bonded to one another to provide heat exchange between thehot and cold streams by placing the channels that make up the flow pathsin close proximity to one another and to provide catalytic reforming ofthe gaseous hydrocarbon-steam stream 174. The stacking may includestacking of end plates, bounding plates and specific configurations ofgaseous hydrocarbon-steam and flue gas plates according to the desiredheat transfer. In general the flow paths for each of the streams may beformed as channels in the plates by etching, milling or other suitableprocess and may be configured to provide for the desired heat exchange,while limiting pressure drop for one or more streams across the PCR. Thechannels on each plate may be configured for single or multiple passheat transfer between the streams, and may be configured to operate inco-flow, cross-flow or counter-flow. In some embodiments, the plates forone of the streams may be configured for multiple passes, while theplates for the other stream are configured for single passes.Preferably, the streams entering and leaving the PCR are maintained attemperature, pressure and composition conditions that avoid or reducemetal dusting conditions within the PCR. The embodiment shown in FIG.9A-E comprises three stages of pre-reforming.

Referring to FIG. 9A-E, in some embodiments, the PCR may comprise one ormore bounding plates 910, one or more flue gas plates 920, one or moregaseous hydrocarbon-steam plates 950, one or more top end plates 970 andone or more bottom end plates 980. For those plates and streams that donot have penetrations through which the flow paths and flow channels areaccessed, headers may be attached, such as welded, over the individualchannel ends at the end of the stacked plates to facilitate deliveryand/or collection of the stream flowing through the relevant channels.In some embodiments, such a header may comprise a portion of pipe ortubing that has been opened on one side to provide for flow of theindividual channels directly into the pipe or tubing. FIG. 9A-E eachinclude insulating cutouts A and FIG. 9C also includes insulatingpenetrations B. Insulating cutouts A span the entire height of the stackof the PCR when the plates are stacked and formed into a PCR and serveto control heat flow and prevent the undesirable flow of heat from thehot portions of streams on a plates to cool portions of the same streamson the same plate via conduction along the plates by providing a regionof reduced heat transfer between the streams. Insulating penetrations 9Bserve the same purpose but are only present on the gaseous hydrocarbonsteam plates 950 and do not span the height of the entire stack.

FIG. 9A shows a bounding plate 910 having a flue gas flow path 911comprising multiple independent flow channels 912 connecting flue gasinlets 913 with flue gas outlets 914. Bounding plate 910 also includesreforming chamber or bed penetrations 915, 916 and 917 and gaseoushydrocarbon stream penetration 918. Bounding plate 910 helps serve tobalance the heat loads and heat flux throughout the stack when formedinto a heat exchanger.

Referring to FIG. 9B, flue gas plate 920 includes reforming chamber orbed penetrations 921, 922 and 923 and gaseous hydrocarbon streampenetration 924. Flue gas plate 920 also includes flue gas flow path 927with flue gas inlets 926 and flue gas outlets 925. Flow path 927 maycomprise one or multiple independent flow channels 928. Though aspecific number of independent flow channels 928, are shown in FIG. 9B,it should be understood that flow path 927 may comprise any suitablenumber of independent flow channels configured appropriately accordingto the individual needs of the system. Furthermore, though FIG. 9B showsflow path 927 as being cross flow or single pass, in some embodimentsflow path 927 may comprise multiple passes, such as from 2 to 20 passes,from 2 to 10 passes or from 2 to 5 passes. Preferably, flow path 925 isa cross flow or single pass flow path.

Referring to FIG. 9C, gaseous hydrocarbon-steam plate 950 includesreforming chamber or bed penetrations 951, 952 and 953 and gaseoushydrocarbon stream penetration 954. Gaseous hydrocarbon-steam plate 950includes gaseous hydrocarbon-steam flow path 955 with gaseoushydrocarbon-steam inlets 956 and reformer stream outlets 957. Flow path955 may comprise one or multiple independent flow channels 958. Though aspecific number of independent flow channels 958, are shown in FIG. 9C,it should be understood that flow path 955 may comprise any suitablenumber of independent flow channels configured appropriately accordingto the individual needs of the system. Furthermore, though FIG. 9C showsflow path 955 as being a combination of multiple cross flow passes andsingle pass cross flow, in some embodiments flow path 955 may comprisemultiple flow passes, such as from 2 to 20 passes, from 2 to 10 passesor from 2 to 5 passes and in other embodiments, flow path 955 maycomprise single pass cross flow, co-flow or counter flow. Preferably,flow path 955 is a combination of multiple cross flow passes and singlepass cross flow during heat exchange, while flowing in a generallycounter-flow or cross flow direction relative to flue gas stream 160. Insome embodiments, flow path 955 comprises multiple cross flow passesbetween inlet 956 and the first reforming chamber or bed penetration951, while flowing in a generally counter-flow direction and single passcross flow between the first and the second combustion chambers and thesecond and the third combustions chambers, while still flowing in agenerally counter-flow direction.

In some embodiments, FIG. 9C also includes gaseous hydrocarbon-steamchannels 960 and reformer stream channels 961. Gaseous hydrocarbon-steamchannel 960 may serve to feed the gaseous hydrocarbon-steam stream 174into the pre-reformer 800 and gaseous hydrocarbon stream penetrations954 and may be supplied via a header that may be welded or connectedover the ends of the individual channels across the stack of platesmaking up the PCR. Gaseous hydrocarbon-steam penetrations 954, alongwith the gaseous hydrocarbon-steam stream penetrations on the otherplates may form a chamber that may be an empty chamber or that mayoptionally contain catalyst to promote additional reforming of thegaseous hydrocarbon-steam stream in the pre-reformer 800. In someembodiments, such as embodiments where channels 960 are not included,the chamber formed from the gaseous hydrocarbon-steam streampenetrations may serve as the inlet for the gaseous hydrocarbon-steamstream 174 into the pre-reformer 800 by feeding the stream through aport attached to an endplate that provides access to the chamber.Similarly, reformer stream channels 961 may serve to collect thereformer stream 811 flowing in the individual plates of pre-reformer 800as stream 174 completes its pre-reforming in the chamber formed byreforming chamber or bed penetrations 917, 923 and 953 and the endplatesfor feeding to the reformer 820. Channels 961 may feed the stream into aheader that may be welded or otherwise connected to the pre-reformerover the ends of the individual channels across the stack of platesmaking up the PCR. Channels 960 and 961 may be configured and sized thesame or differently than channels 958 and there may be the same or adifferent number of channels 960 and 961 compared to channels 958.Generally channels 960 and 961 may independently have the sizesdescribed in Table 1.

Referring to FIG. 9D, top end plate 970 may be a blank plate or a platewith no flow path circuitry and may be insulated to enhance heattransfer and limit heat loss. In some embodiments, top end plate 970 mayinclude inlets and outlets or ports for entry and exit of the variousstreams. In some embodiments, multiple top endplates may be used at eachend. In some embodiments, a single top endplate 970 is used. In otherembodiments, multiple top endplates may be used to provide sufficientthickness for the headers or ports. Similarly, referring to FIG. 9E,bottom end plate 980 may be a blank plate or plates with no flow pathcircuitry and may be insulated to enhance heat transfer and limit heatloss. In some embodiments, bottom end plate 980 may include inlets andoutlets or ports for entry and exit of the various streams, such aspenetration 984 as well as access to the catalyst chambers via accessports 981, 982 and 983 formed when the individual plates are stacked. Insome embodiments, bottom endplate 980 may not include penetration 984.In some embodiments, multiple bottom endplates may be used. In someembodiments, a single bottom endplate 980 is used. In other embodiments,multiple endplates may be used to provide sufficient thickness for theheaders or ports. In some embodiments, the end plates may provide a wallagainst the bounding plate adjacent to the top end plate, serve as lidsto the penetrations and support connection of the relevant streams toPCR 900, such as via ports or headers. Accordingly, the endplates shouldbe thick enough to accommodate the pressures in each of the penetrationsand to support the ports or headers.

When stacked and diffusion bonded or otherwise bonded to form a PCR, thevarious bounding plates 910, flue gas plates 920 and gaseoushydrocarbon-steam plates 950 are preferably aligned such that each ofthe various reforming chamber or bed penetrations 915, 921 and 951, and916, 922 and 952, and 917, 923 and 953 are aligned to form reformingchambers or reforming beds, such as reforming chambers or beds 807, 808and 809. The reforming chambers or beds may be loaded with structured orunstructured catalyst and the reforming reaction may be catalyzed usingany suitable catalyst. In addition, the various plates are preferablyaligned such that gaseous hydrocarbon stream penetrations 918, 924, 954and 984 form a flow access path or chamber for the gaseoushydrocarbon-steam stream.

In addition to aligning the reforming chamber or bed penetrations, thestacking of the plates preferably places flow paths 911, 925 and 955 inclose proximity to one another to facilitate heat transfer between therelevant streams through the walls of independent channels 912, 928 and958. In some embodiments, this heat transfer is represented in FIG. 8 asheat exchangers 804, 805 and 806.

In some embodiments, the plates may be stacked and diffusion bonded orotherwise bonded in any suitable order to form a PCR. In someembodiments, the plates may be stacked in order as follows: at least onetop end plate 970, a bounding plate 910, multiple pre-reforming cells,each pre-reforming cell comprising a flue gas plate 920 and a gaseoushydrocarbon plate 950, followed by one more flue gas plate 920, anotherbounding plate 910 and a bottom endplate 980. Accordingly, the order ofprinted circuit reactor plates in a given stack may have the followingpattern for the active plates (bounding plate 910=B, flue gas plate920=F, gaseous hydrocarbon plate 950=G): B F G F G F G . . . F G F G FB. A perspective view of a flue gas plate 920 and a gaseous hydrocarbonplate 950, i.e. a pre-reforming cell, is shown in FIG. 10. The endplates may be blank plates with no flow path circuitry and may beinsulated to enhance heat transfer and limit heat loss. The end platesmay serve as lids to the chambers and flow access paths formed byalignment of the penetrations and support connection of the relevantstreams to the PCR, such as via ports or headers in fluid connectionwith the chambers and flow paths. Accordingly, the endplates should bethick enough to accommodate the pressures in each of the penetrationsand to support the ports or headers. In some embodiments, a singleendplate is used for each end of the PCR, where the endplate is thickerthan the other plates. In other embodiments, multiple endplates may beused at each end to provide sufficient thickness to support or providefor the headers or ports.

In one specific embodiment for reforming 2 SCMH of natural gas using PSAoff-gas as fuel, the PCR comprises 3 top end plates, followed by abounding plate 910 followed by 11 reforming cells followed by a flue gasplate 920, followed by a bounding plate 910 and 3 bottom end plates.This configuration results in a stacked pre-reformer 800 that is 49.6 mmtall when using plates having a thickness of 1.60 mm. Preferably the PCRmaking up pre reformer 800 is constructed from materials suitable towithstand the pressures and temperatures to which pre-reformer 800 isexposed. In some embodiments, the PCR and therefore pre-reformer 800 maybe constructed from Alloy 800H or Alloy 617.

The individual plates making up the PCR may independently have thethicknesses described in Table 1. In some embodiments, the plates mayeach be 1.6 mm thick. In addition each of the independent flow channels912, 928 and 958 may independently comprise a generally semicircularcross-section and may independently have the dimensions described inTable 1. In some embodiments, each of independent flow channels 912, 928and 958 may have a semicircular cross-section and may have a width ofabout 1.99 mm, a depth of about 1.1 mm and about 0.5 mm ridges.

In some embodiments, the PCR may operate as follows: the gaseoushydrocarbon-steam stream 174 may enter the first stage of reforming 801through gaseous hydrocarbon-steam inlet 956 and the flow access path orchamber formed from alignment of gaseous hydrocarbon-steam penetrations918, 924, 954 and 984 and end plates 970 and 980 and into gaseoushydrocarbon-steam flow path 955 on gaseous hydrocarbon-steam plates 950.The gaseous hydrocarbon-steam flows through gaseous hydrocarbon-steaminlet 956 into independent flow channels 958 on the gaseoushydrocarbon-steam plates 950 where the stream is heated by flue gas thathas entered the PCR on flue gas plates 920 and bounding plates 910 andis flowing in independent flow channels 928 and 912 of flow paths 925and 911 respectively. In the embodiment in FIG. 9A-E, during this firststage of heat exchange, independent flow channels 958 form a flow path955 that has multiple passes and is in cross flow during heat exchangerelative to the flue gas flowing in single pass flow paths 927 and 911.

After the first stage of heating, the gaseous hydrocarbon-steam flowingin channels 958 is directed to reforming chamber or bed 807 formed fromalignment of reforming penetrations 915, 921 and 951 and the endplatesand is partially catalytically reformed. This partially reformed streamthen enters the second stage of pre-reforming 802 where it is heated bythe flue gas stream 160. In this second heating stage, independent flowchannels 958 form a flow path 955 that is a single pass flow pathflowing in cross flow relative to the flue gas flowing in single passflow paths 927 and 911.

After the second stage of heating, the partially reformed stream flowingin channels 958 is directed into reforming chamber or bed 808 formedfrom alignment of reforming penetrations 916, 922 and 952 and theendplates and is partially catalytically reformed. The resultingpartially reformed stream then enters the third stage of pre-reforming803 where it is heated by the flue gas stream 160. In this third heatingstage, independent flow channels 958 form a flow path 955 that is asingle pass flow path flowing in cross flow relative to the flue gasflowing in single pass flow paths 925 and 911.

After the third stage of heating, the partially reformed stream flowingin channels 958 is directed into reforming chamber or bed 809 formedfrom alignment of reforming penetrations 917, 923 and 953 and theendplates and is partially catalytically reformed. The stream leavingreforming chamber or bed 809 leaves the pre-reformer 800 as reformerstream 811 and proceeds to the first stage of reforming in reformer 820.The flue gas stream 160 leaves the pre-reformer 800 and is optionallyre-heated in a combustion chamber 175 before it provides additional heatto water stream 108 in heat exchanger 164 prior to leaving the reformersystem 100.

In some embodiments, gaseous hydrocarbon-steam stream 174 enterspre-reformer 800 at a temperature just below to above the saturatedsteam temperature such as between 200° C. and 270° C., between 210° C.and 260° C., between 215° C. and 250° C., between 220° C. and 240° C. orbetween 225° C. and 240° C. and at a pressure of between 10 bara and 100bara, such as between 10 bara and 90 bara, between 10 bara and 75 bara,between 10 bara and 60 bara, between 10 bara and 50 bara, between 10bara and 40 bara, between 10 bara and 30 bara, between 10 bara and 20bara, between 10 bara and 18 bara, between 11 bara and 17 bara, between12 bara and 16 bara, between 13 bara and 15 bara or between 13.5 baraand 14.5 bara and may leave pre-reformer 800 as reformer stream 811 at atemperature of between 500° C. and 700° C., such as between 510° C. and675° C., between 520° C. and 650° C., between 530° C. and 625° C.,between 550° C. and 600° C. or between 560° C. and 590° C. and at apressure of between 10 bara and 100 bara, such as between 10 bara and 90bara, between 10 bara and 75 bara, between 10 bara and 60 bara, between10 bara and 50 bara, between 10 bara and 40 bara, between 10 bara and 30bara, between 10 bara and 20 bara, between 10 bara and 18 bara, between11 bara and 17 bara, between 12 bara and 16 bara, between 13 bara and 15bara or between 13.5 bara and 14.5 bara.

Flue gas stream 160 may enter pre-reformer 800 at a temperature ofbetween 700° C. and 1050° C., such as between 750° C. and 1000° C.,between 800° C. and 950° C., between 825° C. and 925° C., between 850°C. and 900° C. and at a pressure of less than 1 barg, such as less than0.75 barg, less than 0.50 barg, less than 0.40 barg, less than 0.30barg, less than 0.20 barg, less than 0.15 barg, less than 0.10 barg,less than 0.075 barg, or less than 0.05 barg and may leave pre-reformer800 at a temperature of between 500° C. and 650° C., such as between510° C. and 625° C., between 520° C. and 600° C. or between 530° C. and575° C. and at a pressure of less than 1 barg, such as less than 0.75barg, less than 0.50 barg, less than 0.40 barg, less than 0.30 barg,less than 0.20 barg, less than 0.15 barg, less than 0.10 barg, less than0.075 barg, or less than 0.05 barg.

Referring to FIG. 8, after leaving pre-reformer 800, reformer stream 811enters reformer 820. As shown in FIG. 8, reformer 820 comprises multiplereforming stages, such as 821, 822, 823, 824 and 825 and stagesrepresented by the break 880 which is intended to represent any suitablenumber of stages configured essentially the same as stages 821-825 asdescribed below, each stage including heat exchange from reformer airstream 126 into reformer stream 811 in heat exchangers 831, 832, 833,834 and 835 followed by catalytic reforming of reformer stream 811 inreformers 841, 842, 843, 844 and 845 and reheating of reformer airstream 126 by catalytic combustion of a portion of reformer fuel stream124 in combustion chambers 851, 852, 853 and 855. Reformer fuel stream124 may be supplied in parallel to the individual stages via a fueldistribution network comprising reforming fuel stream 124 and reformingstage fuel streams 861, 862, 863 and 865. Though FIG. 8 shows fivecomplete stages 821, 822, 823, 824 and 825, it should be understood thatany suitable number of reforming stages may be used, such as from 1-40reforming stages, such as from 2 to 35 stages, from 3 to 30 stages, from5 to 25 stages, from 8 to 20 stages or from 10 to 15 reforming stages asrepresented by the break at 880. It should also be noted that the latterstages of reforming may not require reheating of the reformer air stream126 to provide adequate heat for the catalytic reforming and thus one ormore of the latter stages may not include the step of reheating of thereformer air stream 126, may not include combustion chambers or may nothave catalyst in their combustion chambers and/or may not include areforming stage fuel stream. In some embodiments, the last stage ofreforming does not include reheating of the reformer air stream 126. Forexample, though reforming stage 824 shows a combustion chamber 875, itdoes not include a fuel supply and thus combustion chamber 875 may notinclude catalyst and additional combustion may not occur therein.Alternatively, combustion chamber 875 may include catalyst and maycombust any combustible components remaining in reformer air stream 126.Preferably, metal dusting and coking conditions are avoided throughoutthe reforming stages.

In some embodiments, reformer 820 comprises a PCR. The PCR may beconfigured similar to a printed circuit heat exchanger (“PCHE”), withreforming catalyst chambers or beds provided intermittently within theflow path of the reformer stream 811 and combustion catalyst chambersprovided intermittently within the flow paths for the reformer airstream 126 and the reformer fuel stream 124 such that the reformerstream 811 may be alternately heated by the reformer air stream 126 andthen partially reformed catalytically while the reformer air stream 126alternately heats the reformer stream 811 and is re-heated by combustionof a portion of the reformer fuel stream 124. The PCR may be constructedfrom a series of plates that may be combined into a stack and diffusionbonded to one another to provide heat exchange between the hot and coldstreams by placing the channels that make up the flow paths in closeproximity to one another and to provide catalytic reforming of thereformer stream 811 and catalytic combustion of a portion of thereforming fuel stream 124 in the presence of reforming air stream 126.The stacking may include stacking of end plates, bounding plates andspecific configurations of reformer stream plates, reforming air platesand reforming fuel plates.

In general the flow paths for each of the streams may be formed aschannels in the plates by etching, milling or other suitable process andmay be configured to provide for the desired heat exchange, whilecontrolling pressure drops for one or more of the streams across thePCR. The channels on the reforming stream plates and the reforming airstream plates may be configured for single or multiple pass heattransfer between the streams, and may be configured to operate inco-flow, cross-flow or counter-flow. In some embodiments, the plates forone of the reforming streams or reforming air streams may be configuredfor multiple passes, while the plates for the other stream areconfigured for single passes. Preferably, the streams entering andleaving the PCR are maintained at temperature, pressure and compositionconditions that avoid or reduce metal dusting conditions and cokingconditions within the PCR.

An example of the plates that make up an embodiment of such a PCR may befound in FIGS. 11A-F. The embodiments shown in FIGS. 11A-F comprise 14stages of reforming, but it should be understood that any suitablenumber of stages may be used with appropriate modification to thevarious plates shown. Referring to FIGS. 11A-F, the PCR may comprise oneor more bounding plates 1101, one or more reformer plates 1121, one ormore reformer air plates 1141, one or more reformer fuel plates 1161,one or more top endplates 1180 and one or more bottom endplates 1190.

Referring to FIG. 11A, bounding plate 1101 includes reformer streaminlet chamber penetration 1102 and reformer stream outlet chamberpenetration 1103, which may also be the last reforming chamber or bedpenetration, and a flow path 1104 comprising multiple independent flowchannels 1105. In general, bounding plate 1101 will have fewerindependent flow channels 1105 than the number of independent flowchannels on reformer plate 1121. In some embodiments, bounding plate1101 has half the number of independent flow channels as reformer plate1121. As shown in the expanded view of bounding plate 1101 in FIG. 11AA,an example of a single stage of reforming 1110 of the 14 stages includedon bounding plate 1101 includes a reforming chamber or bed penetration1112, a combustion chamber penetration 1114 and a fuel supplypenetration 1113. Bounding plate 1101 helps serve to balance the heatloads and heat flux throughout the stack when formed into a heatexchanger.

Though FIG. 11AA shows reformer chamber penetration 1112 on the righthand sided of bounding plate 1101, it should be understood that thereformer chamber penetrations for the stages of reforming alternatesides along the bounding plate 1101 with fuel supply penetrations 1113from the first or inlet penetrations 1102 to the last or outletpenetrations 1103 and may be started on either side of bounding plate1101. Accordingly, the stages immediately before and after stage 1110would have the reforming chamber or bed penetrations 1112 on the lefthand side of bounding plate 1101 and the fuel supply penetrations 1113on the right hand side of bounding plate 1101. In some embodiments, thestages may be configured differently as suitable for the intended useand the embodiments of the process and apparatus described herein shouldnot be understood to be limited to alternating of the variouspenetrations. For example, where the heat exchange includes one or morepasses, the configuration may change to accommodate these passes.

In operation a portion of the reformer stream 811 flows throughindependent channels 1105 where it recovers heat from the heatedreformer air stream 126 flowing in independent channels 1145 shown inFIG. 11C and FIG. 11 CC and then proceeds to reformer chamberpenetration 1112. Reformer chamber penetrations 1112 (includingpenetrations 1102 and 1103) combine with the corresponding reformerchamber penetrations 1132 (including penetrations 1122 and 1123), 1152,1172 and 1192 on the plates in FIGS. 11B-D and F respectively, to formreformer chambers, such as reformer chambers 841, 842, 843, 844 and 845shown in FIG. 8, where reformer stream 811 is partially catalyticallyreformed. In some embodiments, the chamber formed by inlet penetrations1102 along with the corresponding penetrations on the other plates maybe aligned to form a blank or empty chamber that does not includecatalyst and does not reform reformer stream 811. After being partiallyreformed reformer stream 811 leaves the reformer chamber and recoversheat in the next stage of reforming, until leaving the last stage ofreforming via reformer stream outlet penetrations 1103, at which pointthe reformed stream is combined with the reformed stream leaving thelast stage of reforming on reformer plate 1121 to form syngas stream180.

FIG. 11B shows reformer plate 1121 having reformer stream inletpenetration 1122, and reformer stream outlet chamber penetration 1123,which may also be the last reforming chamber or bed penetration, and aflow path 1124 that comprises multiple independent channels 1125. Asshown in the expanded view of reformer plate 1121 in FIG. 11BB, anexample of a single stage of reforming 1130 of the 14 stages included onreformer plate 1121 includes a reforming chamber or bed penetration1132, a combustion chamber penetration 1134 and a fuel supplypenetration 1133. Though FIG. 11BB shows reformer chamber penetration1132 on the right hand sided of reformer plate 1121, it should beunderstood that the reformer chamber penetrations for the stages ofreforming alternate sides along the reformer plate 1121 with fuel supplypenetrations 1133 from the inlet penetrations 1122 to the outletpenetrations 1123 and may be started on either side of reformer plate1121. Accordingly, the stages immediately before and after stage 1130would have the reforming chamber or bed penetrations 1132 on the lefthand side of reformer plate 1121 and the fuel supply penetrations 1133on the right hand side of reformer plate 1121. In some embodiments, thestages may be configured differently as suitable for the intended useand the embodiments of the process and apparatus described herein shouldnot be understood to be limited to alternating of the variouspenetrations. For example, where the heat exchange includes one or morepasses, the configuration may change to accommodate these passes.

In operation a portion of the reformer stream 811 flows throughindependent channels 1125 where it recovers heat from the heatedreformer air stream 126 flowing in independent channels 1145 shown inFIG. 11C and FIG. 11CC and then proceeds to reformer chamber penetration1132. Reformer chamber penetrations 1132 (including penetrations 1122and 1123) combine with the corresponding reformer chamber penetrations1112 (including penetrations 1102 and 1103), 1152, 1172 and 1192 on theplates in FIGS. 11A, C-D and F to form reformer chambers, such asreformer chambers 841, 842, 843, 844 and 845 shown in FIG. 8, wherereformer stream 811 is partially catalytically reformed. In someembodiments, the chamber formed by inlet penetrations 1122 along withthe corresponding penetrations on the other plates may be aligned toform a blank or empty chamber that does not include catalyst and doesnot reform reformer stream 811. After being partially reformed, thereformer stream 811 leaves the reformer chamber and recovers heat in thenext stage of reforming, until leaving the last stage of reforming andinto reformer stream outlet penetrations 1123, at which point thereformed stream is combined with the reformed stream leaving the laststage of reforming on reformer plate 1101 to form syngas stream 180.

In some embodiments, FIG. 11A-B also include reformer stream inletchannels 1106 and 1126 and reformer stream outlet channels 1107 and1127. Reformer stream inlet channels 1106 and 1126 may serve to feed thereformer stream 811 into the reformer 820 and inlet penetrations 1102and 1122 and may be supplied via a header that may be welded orconnected over the ends of the individual channels across the stack ofplates making up the PCR. Inlet penetrations 1102 and 1122, along withthe corresponding penetrations on the other plates may form a chamberthat may be an empty chamber or that may optionally contain catalyst topromote additional reforming of the reformer stream in reformer 820. Insome embodiments, such as embodiments where channels 1106 and 1126 arenot included, the chamber formed from the inlet penetrations may serveas the inlet for the reformer stream 811 into the pre-reformer 800 byfeeding the stream through a port attached to an endplate that providesaccess to the chamber. Similarly, reformer stream outlet channels 1107and 1127 may serve to collect the syngas stream 180 flowing in theindividual plates of reformer 820 as stream 811 completes its reformingin the chamber formed by reforming chamber or bed penetrations 1103 and1123 and the corresponding penetrations on the other plates and theendplates. Channels 1107 and 1127 may feed stream 180 into a header thatmay be welded or otherwise connected to the pre-reformer over the endsof the individual channels across the stack of plates making up the PCR.Channels 1106, 1107, 1126 and 1127 may be configured and sized the sameor differently than channels 1105 and 1125 and there may be the same ora different number of channels 1106, 1107, 1126 and 1127 compared tochannels 1105 and 1125. Generally channels 1106, 1107, 1126 and 1127 mayindependently have the sizes described in Table 1.

FIG. 11C shows a reformer air plate 1141, having reformer air inlets1142 and reformer air outlets 1143 and a flow path 1144 that comprisesmultiple independent channels 1145. As shown in the expanded view ofreformer air plate 1141, FIG. 11CC, an example of a single stage ofreforming 1150 of the 14 stages included on reformer air plate 1141includes a reformer chamber or bed penetration 1152, a combustionchamber penetration 1154 and a fuel supply penetration 1153. Though FIG.11CC shows reformer chamber penetration 1152 on the right hand sided ofreformer air plate 1141, it should be understood that the reformerchamber penetrations for the stages of reforming alternate sides alongthe reformer air plate 1141 with fuel supply penetrations 1153 from theinlets 1142 to the outlets 1143 and may be started on either side ofreformer air plate 1141. Accordingly, the stages immediately before andafter stage 1150 would have the reforming chamber or bed penetrations1152 on the left hand side of reformer air plate 1141 and the fuelsupply penetrations 1153 on the right hand side of reformer air plate1141. In some embodiments, the stages may be configured differently assuitable for the intended use and the embodiments of the process andapparatus described herein should not be understood to be limited toalternating of the various penetrations. For example, where the heatexchange includes one or more passes, the configuration may change toaccommodate these passes.

In operation, reformer air stream 126 flows through independent channels1145 which may provide heat to a portion of reformer stream 811 flowingin independent channels 1105 on bounding plate 1101 shown in FIG. 11Aand a portion of reformer stream 811 flowing in independent channels1125 shown in FIG. 11B through the walls of the independent channels oneach plate. Reformer air stream 126 then proceeds to combustion chamberpenetration 1154. Combustion chamber penetrations 1154, combine with thecorresponding combustion chamber penetrations, 1114, 1134, 1174 and 1194on the plates in FIGS. 11A-B, D and F to form combustion chambers, suchas combustion chambers 851, 852, 853, and 855 shown in FIG. 8, wherereformer air stream 126 is reheated by catalytic combustion of fuel fromindependent channels 1165 on reformer fuel plates 1161. After beingreheated, reformer air stream 126 leaves the combustion chamber andheats reformer stream 811 in the next stage of reforming, until leavingthe last stage of reforming and into the reforming air penetrationswhere, with reference to FIG. 8, it leaves reformer module 150 as fluegas stream 160.

FIG. 11D shows a reformer fuel plate 1161, having reformer fuel inlets1162, reformer fuel outlets 1163 and flow paths 1164 that comprise oneor more independent channels 1165. Unlike the serial flow of the streamsflowing in the plates shown in FIG. 11A-C, a portion of reformer fuelstream 124 is supplied individually and independently to each of thestages within the reformer in parallel. Accordingly, each stage ofreforming to which fuel is supplied on the reformer fuel plates 1161 hasits own reformer fuel inlets 1162, reformer fuel outlets 1163 and flowpath 1164. In addition, the amount of reformer fuel stream 124 suppliedto each stage may be the same or different from the amount of reformerfuel stream 124 supplied to the other stages. As a result, the reformerfuel inlets 1162, reformer fuel outlets 1163 and flow paths 1164 of eachstage may be configured the same or differently relative to the otherstages. In some embodiments, the amount of reformer fuel stream 124supplied to each stage after the first stage may be reduced relative tothe preceding stage. Furthermore, one or more of the later stages maynot receive any portion of reformer fuel stream 124, as the need toreheat the reformer air stream 126 may be reduced or absent in some ofthe later stages of reforming. An embodiment of a system in which theamount of reformer fuel stream 124 supplied to each successive reformingstage is reduced is discussed below with respect to FIG. 15.

As shown in FIG. 11D, flow paths 1164 may be configured to passivelycontrol the amount of reformer fuel stream 124 supplied to the reformingstages by controlling the size, number and geometry of the independentchannels 1165 and the pressure drops throughout the reforming system100. Multiple reforming fuel outlets 1163 may be used for each stage tomore evenly supply the portion of reformer fuel stream 124 to thecombustion penetration 1174 of that stage. In addition, for some stages,the portion of reformer fuel stream 124 supplied to the stage may beprovided from one or more than one fuel supply penetrations 1173.Accordingly, it should be understood that when referring to a singlestage of reforming, a portion of the fuel supplied to that stage maycome from a fuel supply penetration 1173 physically associated with adifferent stage and that the fuel supply penetrations 1173 may beconfigured to supply fuel to more than one stage. Fuel supplypenetrations 1173, combine with the corresponding fuel supplypenetrations 1113, 1133, 1153 and 1183 on the plates in FIGS. 11A-C andE to form fuel supply flow access paths or chambers.

As shown in the expanded view of reformer fuel plate 1161 in FIG. 11DD,an example of a single stage of reforming 1170 of the 14 stages includedon reformer fuel plate 1161 includes a fuel supply penetration 1173, acombustion chamber penetration 1174 and a reforming chamber or bedpenetration 1172. Though the expanded view of reformer fuel plate 1161shows fuel supply penetration 1173 on the right hand sided of reformerfuel plate 1161, it should be understood that the fuel supplypenetrations alternate sides along the reformer fuel plate 1161 withreforming chamber or bed penetrations 1172. Accordingly, the stagesimmediately before and after stage 1170 would have the fuel supplypenetrations 1173 on the left hand side of reformer fuel plate 1161 andthe reforming chamber or bed penetrations 1172 on the right hand side ofreformer fuel plate 1161. In some embodiments, the stages may beconfigured differently as suitable for the intended use and theembodiments of the process and apparatus described herein should not beunderstood to be limited to alternating of the various penetrations.

In operation a portion of reformer fuel stream 124 flows from the fuelsupply flow access paths or chambers through the fuel inlets 1162 alongflow paths 1164 comprising independent channels 1165, through fueloutlets 1163 and into the combustion chambers 1174 where the portion offuel from reformer fuel stream 124 is catalytically combusted in thepresence of reformer air stream 126, thereby re-heating reformer airstream 126. The byproducts from the combustion of the portion of fuelfrom reformer fuel stream 124 leave the combustion chamber with reformerair stream 126.

In some embodiments, FIG. 11A-D each include reformer air stream inletchannels 1108, 1128, 1142 and 1168 and reformer air stream outletchannels 1109, 1129, 1143 and 1169. Reformer stream inlet channels 1108,1128, 1142 and 1168 may serve to feed the reformer air stream 126 intothe reformer 820 and reformer air inlet penetrations 1115, 1135, 1155and 1175 and may be supplied via a header that may be welded orconnected over the ends of the individual channels across the stack ofplates making up the PCR. Inlet penetrations 1115, 1135, 1155 and 1175may form a chamber that may be an empty chamber that gathers thereformer air stream for feeding into flow path 1144 comprising channels1145. Similarly, reformer stream outlet channels 1109, 1129, 1143 and1169 may serve to feed the flue gas stream 160 flowing in the individualplates of reformer 820 after the final stage of heat exchange andoptional combustion to the piping or tubing feeding the flue gas streamto the pre-reformer 800. Channels 1109, 1129, 1143 and 1169 may feedstream 160 into a header that may be welded or otherwise connected tothe pre-reformer over the ends of the individual channels across thestack of plates making up the PCR. Reformer air stream inlet channels1108, 1128, 1142 and 1168 and reformer air stream outlet channels 1109,1129, 1143 and 1169 may be configured and sized the same or differentlythan channels 1145 and there may be the same or a different number ofreformer air stream inlet channels 1108, 1128, 1142 and 1168 andreformer air stream outlet channels 1109, 1129, 1143 and 1169 comparedto channels 1145. Generally reformer air stream inlet channels 1108,1128, 1142 and 1168 and reformer air stream outlet channels 1109, 1129,1143 and 1169 may independently have the sizes described in Table 1. Byconfiguring the feed of the reformer air stream 126 in this manner, thepressure drop of the stream across the reformer may be minimized.

FIG. 11E shows an example of a top endplate 1180 having fuel supplypenetrations 1183. Top end plate 1180 may be a blank plate or plateswith no flow path circuitry and may be insulated to enhance heattransfer and limit heat loss. In some embodiments, a single top endplate1180 is used. In other embodiments, multiple top endplates 1180 may beused to provide sufficient thickness for the headers or ports thatsupply the fuel. In some embodiments, a header may be provided that isconnected, such as welded, across the length and width of the top plateand that provides for supply of the fuel to each of the fuel supplypenetrations. In some embodiments, this supply may be accomplished byproviding the fuel to the header, where the header is a single openspace that provides access to each of the fuel supply penetrations,which by virtue of their configuration provide the desired pressure dropto achieve the desired passive control of the fuel supply to thecombustion chambers in the reformer. Similarly, as shown in FIG. 11Fbottom end plate 1190 may be a blank plate or plates with no flow pathcircuitry and may be insulated to enhance heat transfer and limit heatloss. In some embodiments, bottom end plate 1190 may include inlets andoutlets for entry and exit of one or more of the various streams as wellas reforming chambers or bed penetrations 1192 and combustion chamberpenetrations 1194, which may have access ports connected thereto. Insome embodiments, multiple bottom endplates may be used. In someembodiments, a single bottom endplate 1190 is used. In otherembodiments, multiple endplates may be used to provide sufficientthickness for headers or ports. In some embodiments, the end platesprovide a wall for the passages on the bounding plate facing the endplate, serve as lids to the penetrations and support connection of therelevant streams to the PCR, such as via ports or headers. Accordingly,in some embodiments, the endplates should be thick enough to accommodatethe pressures in each of the penetrations and to support the ports orheaders. In some embodiments, the various penetrations in the bottomendplates may each be capped with penetration caps, after the plateshave been stacked and formed into a reformer. In some embodiments, thepenetration caps may comprise any suitable material, including thematerial from which the plates are formed and may be connected, such aswelded or otherwise connected to block, seal or cover the penetrationson the bottom endplates.

When stacked and diffusion bonded or otherwise bonded to form a PCR, thevarious bounding plates 1101, reformer plates 1121, reformer air plates1141, reformer fuel plates 1161, tope endplates 1180 and bottomendplates 1190 are preferably aligned such that each of the variousreforming chamber or bed penetrations 1112, 1132, 1152, 1172 and 1192are aligned to form reforming chambers or reforming beds, such asreforming chambers or beds 841, 842, 843, 844 and 845. In addition toaligning the reforming chamber or bed penetrations, the stacking of theplates preferably aligns the fuel supply penetrations 1113, 1133, 1153,1173 and 1183 to form fuel supply flow access paths or chambers andaligns the combustion chamber penetrations 1114, 1134, 1154, 1174 and1194 to form combustion chambers, such as combustion chambers 851, 852,853 and 855. The reforming chambers or beds and the combustion chambersmay be loaded with structured or unstructured catalyst and the reformingreaction and the combustion reaction may be catalyzed using any suitablecatalyst. For those plates and streams that do not have penetrationsthrough which the flow paths and flow channels are accessed, headers maybe attached, such as welded, over the individual channel ends tofacilitate delivery and/or collection of the stream flowing through therelevant channels.

In addition to aligning the various penetrations, the stacking of theplates preferably places flow paths 1104 and 1124 in close proximity toflow path 1144 to facilitate heat transfer through the walls ofindependent channels 1145 into independent channels 1105 and 1125. Insome embodiments, this heat transfer occurs in what are represented inFIG. 8 as heat exchangers, such as heat exchangers 831, 832, 833 and834.

In some embodiments, the plates may be stacked and diffusion bonded orotherwise bonded in any suitable order to form a PCR version of thereformer 820. In some embodiments, the plates may be stacked anddiffusion bonded or otherwise bonded in order as follows: at least onetop end plate 1180, a bounding plate 1101, multiple reforming cells;each reforming cell comprising a reformer air plate 1141, reformer fuelplate 1161, a second reformer air plate 1141 and a reformer plate 1121,and the rest of stack includes in order a reformer air plate 1141, areformer fuel plate 1161, a second reformer air plate 1141, anotherbounding plate 1101 and a bottom endplate 1190. Accordingly, the orderof printed circuit reactor plates in a given stack for some embodimentsof reformer 820 may have the following pattern for the active plates(bounding plate 1101=B, reformer air plate 1141=A, reformer fuel plate1161=F, a reformer plate 1121=R): B A F A R A F A R . . . A F A B. Aperspective view of a reforming cell is shown in FIG. 12.

In one specific embodiment for reforming 2 SCMH of natural gas, reformer820 comprises a PCR having 3 top end plates, followed by a boundingplate 910 followed by 5 reforming cells followed by a reformer air plate1141, a reformer fuel plate 1161, a second reformer air plate 1141,another bounding plate 1101 and 3 bottom end plates. Preferably,reformer 820 comprises a PCR that is constructed from materials suitableto withstand the pressures and temperatures to which reformer 820 isexposed. In some embodiments, reformer 820 may be constructed from Alloy800H or Alloy 617.

The individual plates making up the PCR may independently have thethicknesses described in Table 1. In some embodiments, the plates mayeach be 1.6 mm thick. In addition each of the independent flow channels1105, 1125, 1145, and 1165 may independently comprise a generallysemicircular cross-section and may independently have the dimensionsdescribed in Table 1. In some embodiments, independent channels 1105 onbounding plates 1101 may have a depth of 1.10 mm depth, a width of 1.69mm and 1.00 mm ridges. In some embodiments, independent channels 1125 onreformer plates 1121 may have a depth of 1.10 mm depth, a width of 1.69mm and 1.00 mm ridges. In some embodiments, independent channels 1145 onreformer air plates 1141 may have a depth of 1.10 mm depth, a width of1.69 mm and 0.90 mm ridges. In some embodiments, independent channels1165 on reformer fuel plates 1161 may have a depth of 1.10 mm depth, awidth of 1.69 mm and 0.4 mm ridges.

In some embodiments, when reformer 820 comprises a PCR, the PCR mayoperate as follows: the reformer stream 811 may enter flow paths 1104and 1124 on bounding plates 1101 and reformer plates 1121 a catalystfree reformer chamber formed by alignment of the relevant reformerpenetrations on each of the plates making up the PCR including reformerstream inlet penetrations 1102 and 1122. The reformer stream 811 mayenter the independent channels 1105 and 1125 making up flow paths 1104and 1124 where it is heated by reformer air stream 126 that has enteredthe PCR on reformer air plate 1141 through reformer air inlets 1142 andinto reforming the multiple independent channels 1145 of flow path 1144.Preferably, reformer air stream 126 and reformer stream 811 exchangeheat through the walls of their independent channels 1145, 1105 and 1125while flowing in single pass cross flow yet generally the streamspreferably flow in a co-flow direction as shown in FIG. 8. Thus, duringthe actual heat transfer the streams preferably flow in cross flowrelative to each other, but the flow of both of the streams through thePCR is preferably in a generally co-flow direction.

After receiving heat from the reformer air stream 126, the reformerstream 811 enters reforming chamber or bed 841 formed from alignment ofthe various reforming chamber or bed penetrations on the plates of thePCR where the gaseous hydrocarbon in the reformer stream is partiallycatalytically reformed. Similarly, after heating reformer stream 811reformer air stream 126 enters combustion chamber 851 where it isre-heated by combustion of a portion of the fuel from reformer fuelstream 124. The portion of reformer fuel stream 124 enters the PCRthrough one or more reformer fuel flow access paths or chambers formedby alignment of the relevant fuel supply penetrations on each of theplates making up the PCR and enter independent channels 1165 of flowpath 1164 and through reformer fuel inlets 1162. The portion of thereformer fuel stream 124 flows through independent channels 1165 andinto combustion chamber 851 through reformer fuel outlets 1163 and thefuel is catalytically combusted in the presence of reformer air stream126 to re-heat the reformer air stream 126 for the next stage ofreforming. In this manner, the reformer stream 811 and the reformer airstream 126 are subjected to multiple stages of heat exchange, reforming,and combustion until reformer stream 811 leaves the PCR as syngas stream180 and the reformer air stream 126 leaves the reformer as flue gasstream 160.

A top view of PCR version 900 or pre-reformer 800 and a top view of PCRversion 1300 of reformer 820 are shown in FIG. 13A-B. As shown in, eachof the pre-reforming chambers or pre-reforming beds 1310, 1320, 1330 andreforming chambers or beds 1340 are shown packed with reformingcatalyst. Similarly, each of combustions chambers 1350 are shown packedwith catalyst. In this version of PCR 1300, top plates 1360 also includefuel supply penetrations 1362 which help to form fuel supply chambers1364. Accordingly, in this embodiment of PCR 1300, access to each of thechambers may be obtained through the top plates 1360.

The various PCHE's and PCR's described herein may comprise plates thatinclude independent flow channels for the various streams. The platesfor each of the PCHES's and PCR's may, independently for each plate orflow channel, have the dimensions described in Table 1:

TABLE 1 Example PCHE and PCR Plate Thicknesses and Flow ChannelDimensions CHANNEL DIMENSIONS Ridge Width between Width (millimeters)Depth (millimeters) channels (millimeters) Preferred ranges ofdimensions 0.6 to 4.5 0.3 to 2.5 0.2 to 2.5 Example ranges of dimensions0.8 to 3.25, 1 to 3, 1.1 0.4 to 2, 0.5 to 1.5, 0.3 to 2, 0.5 to 1.2, 0.7to to 2.5, 1.2 to 2.25, 1.3 0.6 to 1.4, 0.75 to 1.1, 0.8 to 1.1, 0.8 to1.0, to 2, 1.4 to 1.75, 1.4 1.25, 1 to 1.25 0.3 to 0.8, 0.3 to 0.5 to1.6 PLATE THICKNESSES Plate Thickness (millimeters) Preferred range ofthicknesses 0.5 to 3 Example ranges of thicknesses 0.75 to 2.9, 0.9 to2.5, 1 to 1.75, 1.1 to 1.6, 1.25 to 1.5

In one embodiment for reforming 2 SCMH of natural gas using PSA off-gasas a fuel, efficient operation of the reformer module 150 whileremaining within the material design temperatures may have thetemperature profiles for reforming and combustion that appearapproximately like those shown in FIG. 14. Though not representingactual data, FIG. 14 shows a graph 1400 of a desired trend in thetemperature profile of reformer stream 811 and reformer air stream 126as they proceed through 14 stages of reforming (with the last reformingchamber or bed and combustion chamber omitted) with passive control ofthe fuel supply to each stage of combustion such that the amount of fuelsupplied decreases from stage to stage. As shown, it is believed thatthe temperature of the reformer stream 811 as it is reformed in each ofthe reforming chambers or beds 841, 842, 843 etc. of a 14 stage reformeris likely to appear approximately as shown by line 1401 and thetemperature of reformer air stream 126 is likely to appear as it isheated and exchanges heat with reformer stream 811 as shown by line1410. As shown, the average temperature difference between reformerstream 811 and reformer air stream 126 for each stage should decreasefrom stage to stage and the temperature of reformer stream 811 shouldrise from stage to stage. Preferably, the rise in temperature ofreformer stream 811 should be preceded by an increase in the partialpressure of hydrogen in the reformer stream 811 as a result of thereforming. By leading the rise in temperature with an increase inhydrogen content in the reformer stream 811, coking and metal dustingconditions should be reduced or avoided. As a result of the increasingreformer stream temperature from stage to stage, the fuel requirementsfor each successive stage of this embodiment should be reduced betweenthe stages as the heat load required to re-heat the reformer stream 811and to re-heat the reformer air stream 126 should be reduced from stageto stage. Preferably, as shown in FIG. 14, the temperature of thereformer stream and the reformer air stream will converge to anasymptote somewhere above 800° C.

In some embodiments, the supply of fuel and/or air to each of the stagesof reforming may be passively controlled by controlling the pressure andthe pressure drops in the air and the fuel streams throughout thereformer system 100. By passively controlling the supply of fuel to eachof the stages, the amount of heat generated by combustion of the fuel iscontrolled, thereby controlling the amount of heat provided to thereformer air stream 126 and ultimately the reformer stream 811 andassociated reforming chambers or beds. The pressure of the fuel at theinlet in a given line and the pressure drop across the length of theline determines the volume of fuel that is delivered through that lineper unit time. Pressure drop may be adjusted in a given fuel line by,for example, varying the length of the fuel line, varying the tortuosityof the flow path, i.e. the number and severity of turns in the fuelline, varying the number of fuel lines and/or varying thecross-sectional area of the fuel line. Changing one or some of thesefuel line characteristics thus adjusts the amount of “resistance”encountered by the flow of fuel in a given fuel line en route to acombustion chamber, and may thus passively control the amount of fuelprovided per unit time.

The efficiency of the reforming process is temperature dependent becausethe methane conversion achieved depends on the maximum temperatureachieved. It is also desirable to limit the upper temperature of themetal that forms the physical structure of the reformer. Therefore, bycontrolling the amount of fuel fed to each successive combustion chamberby configuring the fuel lines specifically for each reforming stage, themetal temperatures may be controlled while providing for stage by stageincreases in reforming temperature, thereby increasing the efficiency ofthe overall reformer system 100.

It is preferred that the control provided by tuning the fuel lineconfigurations is passive. In other words, the fuel line configurationsthemselves provide the control without the need for affirmative controlmechanisms. To this end, it is preferred that the fuel lines beconfigured specifically for the parameters of a particular system. Forexample, in the PCR version of reformer 820 described with respect toFIG. 11A-F, each independent channel 1165 which feeds fuel to acombustion chamber may be independently etched or otherwise formedaccording to a desired fuel line configuration for that channel toprovide a desired resistance. After the system is manufactured with thefuel lines so configured, additional active control mechanisms arepreferably unnecessary. By providing for such passive control, reformersystem 100 may be simpler and smaller because the use of active flowmeasurement and control devices is limited or avoided resulting in costand design benefits and flexible turndown ratios.

In some embodiments, to reduce the number of parameters that may need tobe considered in arriving at the appropriate resistance to be providedby each independent channel 1165, and for ease of manufacturing thechannels, it is preferred that independent channels 1165 feeding therespective combustion chambers each have the same cross-sectionaldimension. It is also preferred that all independent channels 1165 beconfigured for laminar flow so that the pressure drop is a directfunction of flow for all of the channels. As such, due to the linearvariation in flow relative to pressure drop, the ratios of the fuel flowand air flow at each stage of combustion may remain relatively constanteven during significant turndown of reformer system 100.

The delivery of air and fuel to the combustion chambers, such ascombustion chamber 821 is balanced by the design of plates 1141 and1161. Moreover, the pressure of the air arriving through air lines 1145and the pressure of the fuel arriving through independent channels 1165match or self adjust to match at the combustion chamber to produce thedesired amount of combustion for that particular chamber. This balancingof the pressures in turn provides the appropriate amount of heat to thereforming reactants as they enter the associated reforming chamber orbed. It is preferred that the pressure drops in each line areestablished so that the overall fuel pressure is just above atmospheric.However, other pressure drops may be established and are within thescope of some embodiments.

FIG. 15 is a diagram of the flow resistances within the air and fuellines that supply an embodiment of the reformer module. The flowresistances within this network as shown in FIG. 15 are preferably tunedso that the amount of fuel delivered to each combustion stage throughsuccessive reforming stage fuel streams 861, 862, 863, etc., diminishesover the length of the reformer despite the fact that the pressure dropdriving the fuel flow increases. This reduction over the length of thereformer results in the diminishment of reforming that occurs in eachsuccessive reforming stage and the increase in temperature of thereforming stream in each successive reforming stage. FIG. 15 shows theflow resistance in the air and fuel lines associated with the individualcomponents through which the fuel lines flow and is discussed withreference to streams and components described with respect to FIG. 1. Asshown, air feed stream 106 is split into air feed stream 107 andcombustion air stream 114. Combustion air stream 114 experiences flowresistance 1515 associated with valve 115 a, before it proceeds intosyngas heat recovery heat exchanger 110, where it experiences flowresistance 1511 and leaves syngas heat recovery heat exchanger 110 ascombustion air stream 1514. Similarly, air feed stream 107 and fuel feedstream 105 proceed into syngas heat recovery heat exchanger 110 wherethey experience flow resistances 1512 and 1510 respectively.

After leaving syngas heat recovery heat exchanger 110, combustion airstream 1514 and fuel feed stream 105 are combined to form fuel/airmixture stream 118. A passively controlled portion of fuel/air mixturestream 118 corresponding to air preheat mixture 117 experiencesresistance 1520 as it is split from fuel/air mixture 118 to be combustedin the presence of air feed stream 1508 in air pre-heater 122. Theremaining portion of fuel/air mixture 118, fuel preheat mixture 119, ispartially catalytically combusted in fuel pre-heater 120, where itexperiences flow resistance 1530 and becomes reformer fuel stream 124.In air pre-heater 122, air feed stream 107 is heated by catalyticcombustion of the fuel in air preheat mixture 117, experiences flowresistance 1522 and then experiences flow resistance 1525 as it entersreformer module 150 becomes reforming air stream 126. Flow resistance1525 is associated with a non-negligible flow resistance which isphysically after air pre-heater 122 at the entrance to the reformerblock.

At this point in FIG. 15, the reformer fuel stream 124 and reformer airstream 126 enter reformer 820. As shown, reformer air stream 126experiences resistance 1540 in heat exchanger 831 in the first stage ofreforming in reformer 820 becoming reformer air stream 1550. Afterleaving heat exchanger 831, reformer air stream 1550 is joined with apassively controlled portion of reformer fuel stream 124, such asreforming stage fuel stream 861, and the fuel is subsequently combustedin combustion chamber 851 to reheat reformer air stream 1550. Thepassively controlled portion of reformer fuel stream 124 experiencesflow resistance 1560 prior to joining reformer air stream 1550 as aresult of the flow control. Reformer air stream 1550 experiences flowresistance 1541 in heat exchanger 832 in the next stage of reforming,leaves heat exchanger 832 as reformer air stream 1551 and is combinedwith a passively controlled portion of reformer fuel stream 124, such asreforming stage fuel stream 862, which experiences flow resistance 1561prior to combining with reformer air stream 1551. Reformer air stream1551 is then reheated in combustion chamber 852 and experiences flowresistance 1542 in heat exchanger 833 in the next stage of reformingbecoming reformer air stream 1552. After leaving heat exchanger 833,reformer air steam 1552 is combined with a passively controlled portionof reformer fuel stream 124, such as reforming stage fuel stream 863,which experiences flow resistance 1562 prior to combining with reformerair stream 1552, and is reheated by combustion of the fuel in combustionchamber 853.

In this manner the flow resistance network for the air and fuel streamsoperates through any suitable number of stages represented by 880 inFIG. 8 and experiences the flow resistances represented by brackets 1570and 1571 in FIG. 15. Just prior to the last stage of reforming, reformerair stream 1553 is combined with a passively controlled portion ofreformer fuel stream 124, such as reforming stage fuel stream 865, whichexperiences flow resistance 1565 prior to combining with reformer airstream 1553, and is reheated by combustion of the fuel in combustionchamber 855. After being reheated, reformer air stream 1552 exchangesheat one last time with the reformer stream before leaving reformer 820as flue gas 160.

In the reformer of FIG. 15, there are two routes to any point at whichfuel and air may mix, and in operation of the equipment, the flows downthe branches self-adjust so that the pressures at the mixing pointsmatch. Thus, in some embodiments the following constraints may be placedupon the design pressures and pressure drops of the components in thefuel/air flow resistance network shown in FIG. 15 (P_(x) indicates thepressure in x line, while ΔP_(x) indicates the pressure drop due to thex reference numeral resistance shown in FIG. 15; P_(105(hot)) is thepressure in stream 105 after experiencing resistance 1510 in syngas heatrecovery heat exchanger 110 and P_(105(cold)) is the pressure in stream105 prior to entering syngas heat recovery heat exchanger 110):

P _(105(hot)) =P _(105(cold)) −ΔP ₁₅₁₀ =P ₁₀₆ −ΔP ₁₅₁₅ −ΔP ₁₅₁₁

P ₁₅₀₈ =P ₁₅₁₈ −ΔP ₁₅₂₀ =P ₁₀₇ −ΔP ₁₅₁₂ −ΔP ₁₅₂₂

P ₁₅₅₀ =P ₁₅₁₈ −ΔP ₁₅₃₀ −ΔP ₁₅₆₀ =P ₁₅₀₈ −ΔP ₁₅₂₅ −ΔP ₁₅₄₀

P ₁₅₅₁ =P ₁₅₁₈ −ΔP ₁₅₃₀ −ΔP ₁₅₆₁ =P ₁₅₅₀ −ΔP ₁₅₄₁

P ₁₅₅₂ =P ₁₅₁₈ −ΔP ₁₅₃₀ −ΔP ₁₅₆₂ =P ₁₅₅₁ −ΔP ₁₅₄₂

P ₁₅₅₃ =P ₁₅₁₈ −ΔP ₁₅₃₀ −ΔP ₁₅₆₅ =P _(PREVIOUS STAGE) −ΔP_(HEAT EXCHANGER)

-   -   PREVIOUS STAGE

In one embodiment for reforming 2 SCMH of natural gas using PSA off-gasas a fuel, a suitable solution for the pressure drops satisfying theabove constraints in a PCR reformer comprising 14 stages of reforming isshown in Table 2 below using the reference numerals used in FIGS. 1 and8 to identify the components or streams within which the pressure dropoccurs where appropriate. Note that for the stages of reformingrepresented by the brackets 836 and 826 in FIG. 8, the relevant heatexchanger/combustion stages or reforming stage fuel streams areidentified by the reference numerals are 836(x) and 826(x) respectively,where x is a letter of the alphabet starting at “a” and proceeding downthe alphabet for each successive stage of reforming. Thus for the firststage of reforming represented by brackets 836 and 826, the reformer airstream is represented by 836(a) and the reforming stage fuel supply isrepresented by 826(a) and so on.

TABLE 2 Examples of Suitable Pressure Drops in the Fuel and Air Streamsin One Embodiment of the Reforming System Component/Stream ΔP (kPa)Component/Stream ΔP (kPa)  110/107 3.08 117 1.07  110/105 1.05 861 1.93115a/114 0.00 862 2.32  110/114 1.87 863 2.73  122/107 0.10 826(a) 3.17 150/126 0.09 826(b) 3.62  126/831 0.37 826(c) 4.10 832 0.40 826(d) 4.61833 0.43 826(e) 5.12 836(a) 0.45 826(f) 5.66 836(b) 0.48 826(g) 6.23836(c) 0.50 826(h) 6.77 836(d) 0.52 826(i) 7.33 836(e) 0.54 865 8.04836(f) 0.56 836(g) 0.57 836(h) 0.59 836(i) 0.60 835 0.61

In one embodiment for reforming 2 SCMH of natural gas using PSA off-gasas a fuel comprising 14 stages of reforming and starting with the fuelin line 117 sent to combustion chamber 122 to reformer air stream 126and proceeding through each of the successive reforming stage fuelstreams 861, 862, 863, the proportion of the fuel stream 118 sent intoeach line may be as indicated in Table 3 below. Note that for the stagesin FIG. 8 represented by bracket 826, the reference numerals used are826(x) where x is a letter of the alphabet starting at “a” andproceeding down the alphabet for each successive stage of reforming.

TABLE 3 Example of Fuel Distribution in a 14 Stage Reformer Fuel Stream% of Fuel Flow 117 18.6% 861 10.4% 862 9.8% 863 8.9% 826(a) 8.1% 826(b)7.7% 826(c) 6.9% 826(d) 6.3% 826(e) 5.5% 826(f) 4.9% 826(g) 4.1% 826(h)3.5% 826(i) 2.8% 865 2.5%

Preferably, a high degree of precision is not required in the rate offuel distribution in some embodiments of the reformer, but in someembodiments, the rate of fuel addition to each stage generally falls, asthe reformer temperature increases, in order to keep reformingtemperatures below, but close to, the material design temperature forthe equipment. In some embodiments, the design temperature may be on theorder of 820° C. or higher. Higher temperatures may favor methaneconversion within the reformer, but may also create more severeoperating conditions for the materials of construction. Because the heattransfer coefficients of the gases on the reforming side areconsiderably higher than those on the combustion side, the overalltemperature of the materials of construction tends to stay close to thereforming gas temperature, and hence, in some embodiments the combustiongas temperatures may exceed the material design temperature.

In order to achieve the fuel/air mixtures throughout the reformer whichwill achieve the desired temperature profiles, the heat exchange andcombustion components are preferably designed to fulfill their primaryfunctions while ensuring that the pressure drops associated with eachcorrespond to those required for sound fuel/air mixing. Preferably, thepressure drops for the air and fuel streams across reformer 820 are low,such as less than 0.50 bar, less than 0.30 bar, less than 0.25 bar, lessthan 0.20 bar, less than 0.175 bar, less than 0.15 bar, less than 0.125bar or less than 0.10 bar or on the order of 0.10 bar or less in totalto avoid inefficiencies associate with large blower power consumption.In addition, the entering fuel feed stream 104 may also be pressure-dropsensitive. For example, where fuel feed stream 104 is the off-gas from aPSA system a high fuel pressure drop, requiring high fuel inletpressure, may lower the efficiency of the PSA system.

In some embodiments, it is desirable that the flow distribution selectedand the corresponding plate configurations are suitable for a largerange of turndown conditions. This may be accomplished by designing therelevant reformer plates, heat exchangers and combustion chambers andthe relevant flow paths for the fuel and air streams such that thepressure drop is essentially proportional to the flow rates (i.e., thatthe flow is essentially laminar; in straight passages, flow isessentially laminar when the Reynolds Number is less than 2000). Bymaintaining laminar flow, sound fuel distribution may be maintained tovery low turndown conditions, as shown in Table 4 below for 10% capacityoperation of an embodiment for reforming 2 SCMH of natural gas using PSAoff-gas as a fuel comprising 14 stages of reforming when compared to thedesign capacity. The data in Table 4 assumes that the air flow is variedproportionately to the capacity, but no further control of the fuel/airsystem is required.

TABLE 4 Comparison of Fuel Flow between Design Capacity and Turndown to10% of Capacity % of Fuel Flow % of Fuel Flow (10% Fuel Stream (DesignCapacity) of Capacity) 117 18.6% 18.3% 821 10.4% 8.8% 822 9.8% 8.9% 8238.9% 8.6% 826(a) 8.1% 8.1% 826(b) 7.7% 7.8% 826(c) 6.9% 7.2% 826(d) 6.3%6.7% 826(e) 5.5% 6.0% 826(f) 4.9% 5.3% 826(g) 4.1% 4.5% 826(h) 3.5% 3.9%826(i) 2.8% 3.1% 865 2.5% 2.8%

In PCR embodiments of the reformer 820, the reformer design may be afour way balance between air pressure drop in the reformer air plate1141, fuel pressure drop in the reformer fuel plate 1161, the heatrequired by the endothermic reforming reaction in the reforming chambersor beds and limiting the maximum temperature produced in the combustionchambers to temperatures suitable for the materials of construction. Tosimplify the surrounding system requirements, the reformer fuel plate1161 and reformer air plate 1141 are preferably configured to provide areduced or minimum pressure drop. As mentioned above, the air and fuelpreferably are delivered to the combustion chambers at slightly aboveatmospheric pressure, preferably eliminating the need for fuelcompression to accomplish the matching of the four variables and therebyavoiding the associated added cost, complexity and unreliability.

In some embodiments, therefore, the design of the independent channels1165 may control the amount of fuel being delivered into each of therespective combustion chambers with only one exterior variable in termsof fuel supply having to be controlled, and that is pressure of the fuelas it is being provided to the fuel manifold that feeds each of the fuelsupply flow access paths or chambers formed from the fuel supplypenetrations. The fuel pressure is preferably controlled to maintain thereformer air stream temperature at a level to limit the maximum overallreformer temperature while supplying the heat required by theendothermic reforming reaction. The need for compression of the fuel ispreferably eliminated by designing all of the independent channels 1165for minimum pressure drop.

The fuel distribution system described above provides several benefitsover the prior art. For example, the metered addition of fuel to eachstage preferably limits the heat which may be added to each stagethereby eliminating the balance of combustion, heat transfer andreforming reaction both radially and axially that must be achieved intubular reformers. Furthermore, the inter-stage heat exchangers are ofmicrostructure (PCHE) construction, which supports higher heat transfercoefficients, minimizes equipment size and high alloy usage therebyreducing cost, and may be configured with a large face area and shortflow path for low pressure drops. In addition the heat exchangers arereadily characterized by engineering analysis without the need forexpensive product full scale tests to validate performance.

In a preferred embodiment, a cross-flow arrangement is used for the heatexchange aspect of reformer 820 and a co-flow arrangement may be usedfor the reforming aspect of reformer 820. The use of a cross-flowarrangement in the heat exchange aspect may permit a higher proportionof the PCR plate area to be devoted to heat exchange duties relative tothat achievable with co-flow or counter-flow arrangements, includingthose employing multiple passes. To this end, the cross-flow heatexchanger component of reformer 820 may be coupled with the co-flowreforming chamber or bed component to produce satisfactory temperatureprofiles for the reformer stream as it travels from one reformingchamber or bed to the next within the series of reforming stages.

A potential issue with this cross flow configuration relates to thepossible variation in the temperature at the outlet of the heatexchanger of each stage because a significant variation in the heatexchanger outlet temperature would result in a wide variation inreaction characteristics in the associated downstream reformer chamberand catalyst. Simulation studies of the eighth heat exchange stage of anembodiment for reforming 2 SCMH of natural gas using PSA off-gas as afuel comprising 14 stages of reforming, without considering wall heatconduction and assuming that the fluid enters the heat exchanger at auniform temperature of about 730° C. showed that the fluid exited theheat exchanger at a temperature range of about 765° C. to 825° C. asshown in FIG. 17. Such a wide variation of the heat exchanger outlettemperature could result in a wide variation in the reforming reactioncharacteristics. However, when the effect of wall heat conduction wasincluded, the heat exchanger outlet temperature range for the eighthheat exchange stage was significantly less, as shown in FIG. 18, e.g.,on the order of about 15° C., or from about 780° C. to about 795° C. Inboth FIG. 17 and FIG. 18, with temperature along the z axis, the x and yaxes represent the dimensions of the cross flow heat exchanger with thereformer air stream flowing along the shorter axis from upper right tolower left and the reformer stream flowing along the longer axis fromlower right to upper left in cross flow relative to the reformer airstream.

This narrow exit temperature range may result from the fact that thewalls of the heat exchanger in some embodiments are preferably thickerthan those of typical finned heat exchangers. As such, it is believedthat there is lengthwise conduction along the wall which serves toreduce the range of exit temperatures. Thus, it is preferred to usesimple cross flow contact in the heat exchangers which allows higherutilization of the plates for heat exchange.

In other embodiments of some PCRs, the reformer air stream and thereformer stream may generally be configured in a counter-flowarrangement but may employ a number of cross-flow passes to achieve thecounter-flow effect. In this situation, to achieve the counter-floweffect, an amount of plate area may be inactive for heat transfer. Tothis end, reforming gas may be led from each reforming bed to the faredge of the inter-stage heat exchanger before it enters the heatexchanger, and is then led from the near end of the heat exchanger tothe succeeding reforming bed. However, the areas consumed in leading thereformer stream between the far and near ends of the heat exchanger toand from the reforming beds may be ineffective for heat exchange, andmay thus compromise the efficiency of plate material usage of thereformer. Also, multi-passing the reformer stream at each stage maylimit the width of each plate element, if pressure drop were not tobecome excessive, and thereby compound the loss of efficiency ofreformer material utilization as the proportion of plate area which isineffective for heat exchange is held high. Accordingly, thoughworkable, such a configuration is not the preferred configuration.

The use of cross-flow heat exchange preferably avoids the need to leadthe reformer stream from one end of the heat exchanger to the other thatexists to achieve counter-flow heat exchange characteristics. As such,the use of cross-flow generally decreases the amount of plate arearequired for heat exchange. Furthermore, by reducing the number ofpasses, the pressure drop across the heat exchangers is decreased whichin turn decreases the number of channels needed. The cross-flowarrangement also preferably allows the use of wider plate elementswithout generating undue pressure drop on the reforming side, such asthe plates shown in FIG. 16 described below.

The use of an overall co-flow configuration for the reforming aspect ofthe process is believed to decrease temperature control requirements ofthe reformer because as the reforming air and reformer streams flow inthe same direction over the length of the co-flow configuration, theirtemperatures will tend to converge. Thus, the control of the exittemperature of one of the streams results in the exit temperature ofboth streams being controlled.

FIG. 19 shows the composite hot and cold enthalpy curves for anembodiment of the reformer system. Curve 1910 represents the compositeheat curve for the hot streams of the process, i.e., those streams whichare cooled in heat exchangers, and curve 1920 is the composite curve forthe cold streams of the process. The closest vertical approach of thecurves is approximately 34° C. and may be referred to as the temperature“pinch”. Because heat cannot flow from cold to hot streams (2^(nd) Lawof Thermodynamics), the highest possible heat recovery efficiency occursfor a pinch of zero. Thus, the smaller the pinch, the higher the overallheat recovery efficiency. In this regard, a pinch of 34° C. is quitesmall, especially considering the fact that one of the streams involvedin heat transfer is low pressure air or flue gas having poor heattransfer characteristics. Note that in addition to the heat recoveryefficiency the steam ratio and the methane conversion also bear on theoverall efficiency of the process, as reflected in the formula describedherein. Ideally, to avoid efficiency loss, heat should not betransferred across the pinch (from above the pinch to below the pinch)in any heat exchanger. Some embodiments of the process or apparatuslimit this occurrence by the process schemes, though in someembodiments, this transfer does occur to a minor extent in heatexchanger 164.

It should be noted that the fourteen stage embodiment of reformer 820described above with respect to FIGS. 11-12 is only an example and isnot intended to limit the embodiments of the reformer. Nor is itnecessary that the number of reforming and combustion stages should beequal. In fact, different plate sizes, configurations and/or the use ofany suitable number of plates and reforming and combustion chambers sothat reformer 820 may be scaled up or down to meet process requirementsare specifically contemplated. Indeed, the printed circuit reformerdesign of some embodiments of reformer 820 allows reformer 820 to bereadily scaled up or down without the significant cost associated withscaling up or down a typical tubular reformer. For example, wheregreater reforming capacity is required, the size of the reformer 820 maybe increased by adding more plates or cells to the stack.

As another example for increasing capacity, the plates may be increasedin size as shown in FIG. 16 by expanding the plates in a side waysdirection rather than increasing the number of plates in the stack. Asshown in FIG. 16, bounding plates 1601, reformer plates 1621, reformingair plates 1641 and reformer fuel plates 1661 may be configuredessentially as a sideways mirror image combination of two of thecorresponding plates discussed previously with respect to FIGS. 11A-D.As shown, each plate has two independent flow paths 1604 and 1608, 1624and 1628, 1644 and 1648 and 1664 and 1668 respectively that share acentral set of reforming chamber or bed penetrations and fuel supplychamber penetrations 1615 and 1616, 1635 and 1636, 1655 and 1656 and1675 and 1676 respectively. Because the chambers formed from the centralset of penetrations are shared, they and the penetrations that form themare correspondingly bigger than the chambers formed from outerindependent reforming chamber or bed penetrations and fuel supplychamber penetrations 1612 and 1613, 1632 and 1633, 1652 and 1653 and1672 and 1673, which may generally correspond to the reforming chamberor bed and fuel supply chamber penetrations discussed above with respectto FIGS. 11A-11D. Each of the plates also includes two sets ofcombustion chamber penetrations 1614 and 1618, 1634 and 1638, 1654 and1658 and 1674 and 1678 respectively which may generally correspond tothe combustion chamber penetrations discussed above with respect toFIGS. 11A-11D.

It should also be understood that the plates of a PCR corresponding toreformer 820 may also be lengthened or shortened to include more orfewer stages of reforming. Furthermore, it should also be understoodthat similar modifications such as those described above may be made tothe pre-reformer and any of the heat exchangers described in here thathave PCHE construction.

In some embodiments, the temperatures and pressures of some of thevarious streams are interrelated and may have the properties as shown inthe following tables 5-8 with reference to the configuration for thereforming system shown in FIG. 1 and FIG. 8, with the combustion airstream 114 combining with fuel feed stream 105 inside syngas heatrecovery heat exchanger 110. In some cases the values are presentedrelative to other values in the Tables, such as for example “relative tothe reforming pressure”, “relative to the reforming temperature”,“relative to atmospheric pressure” or “relative to saturated steamtemperature” in which case the presented values may be above or below(“+xxx”/“−yyy”) or a multiple of (“times”) the identified property,showing the interrelatedness of the properties. In addition, in somecases the values presented may refer to a specific physical parametersuch as “above dew point” or “above freezing point” in which case theidentified stream should meet the requirement based on the identifiedphysical parameter of the stream. “Reforming pressure” or “reformingtemperature” in the tables refer to the properties associated withsyngas stream 180. It should be understood that the values presented areby way of example only and that different configurations of thereforming system may be used that may have different conditions in oneor more of the relevant streams.

TABLE 5 Temperature and Pressure Properties of Some Process Streams ofan Embodiment According to FIG. 1 Temperature (° C.) Pressure (bara)Streams 180, 170 & 182 - “reforming temperature” or “reforming pressure”Preferred range of 700 to 1000 5 to 120 conditions Example ranges of 750to 950, 900 to 1000, 800 to 900, 700 10 to 80, 50 to 100, 40 to 60, 30to conditions to 800, 760 to 900, 50, 10 to 40, 15 to 30, 5 to 20, 5 to780 to 820 10, 10 to 15 Stream 174 Preferred range of Relative tosaturated steam temperature: Relative to reforming pressure: conditions−10 to +100 1.25 to 1 times Example ranges of Relative to saturatedsteam temperature: Relative to reforming pressure: conditions −0 to +80,+10 to +70, +20 to +50 1.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to1.02 times Stream 811 Preferred range of 500 to 700 Relative toreforming pressure: conditions 1.25 to 1 times Example ranges of 520 to680, 530 to 600, 540 to 560 Relative to reforming pressure: conditions1.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to 1.02 times Stream 160immediately prior to entering pre-reformer 800 Preferred range ofRelative to reforming temperature: Relative to atmospheric pressure:conditions +10 to +50 1.25 to 1 times Example ranges of Relative toreforming temperature: Relative to atmospheric pressure: conditions +12to +40, +15 to +30, +18 to +25 1.2 to 1.01 times, 1.15 to 1.01 times,1.1 to 1.02 times Stream 190 Preferred range of 200 to minimum metaldusting Relative to reforming pressure: conditions temperature 0.75 to 1times Example ranges of 250 to 450, 300 to 420, 350 to 400 Relative toreforming pressure: conditions 0.8 to 0.9999 times, 0.85 to 0.9999times, 0.95 to 0.999 times, 0.99 to 0.999 times

TABLE 6 Temperature and Pressure Properties of Some Process Streams ofan Embodiment According to FIG. 1 Temperature (° C.) Pressure (bara)Stream 189 Preferred range of 250 to 350 Relative to reforming pressure:conditions 0.75 to 1 times Example ranges of 260 to 340, 280 to 330,Relative to reforming pressure: conditions 290 to 310 0.8 to 0.9999times, 0.85 to 0.9999 times, 0.95 to 0.999 times, 0.99 to 0.999 timesStream 191 Preferred range of 100 to 200 Relative to reforming pressure:conditions 0.75 to 1 times Example ranges of 120 to 180, 130 to 170,Relative to reforming pressure: conditions 130 to 150 0.8 to 0.9999times, 0.85 to 0.9999 times, 0.95 to 0.999 times, 0.99 to 0.999 timesStream 192 Preferred range of 100 to 200 Relative to reforming pressure:conditions 0.7 to 0.999 times Example ranges of 110 to 180, 115 to 160,Relative to reforming pressure: conditions 120 to 150 0.8 to 0.999times, 0.85 to 0.999 times, 0.95 to 0.99 times, 0.98 to 0.99 timesStream 102 entering syngas heat recovery heat exchanger 110 Preferredconditions Above dew point to Relative to reforming pressure: belowstream 190 1.25 to 1 times temperature Example ranges of −40 to 350, −10to 250, 0 Relative to reforming pressure: conditions to 200, 10 to 150,15 to 1.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to 1.03 50 times Stream102 leaving syngas heat recovery heat exchanger 110 Preferred conditionsRelative to syngas feed Relative to reforming pressure: stream 190temperature: 1.25 to 1 times −20 to −100 Example ranges of Relative tosyngas feed Relative to reforming pressure: conditions stream 190temperature: 1.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to 1.03 −25 to−90, −25 to −50, times −25 to −40

TABLE 7 Temperature and Pressure Properties of Some Process Streams ofan Embodiment According to FIG. 1 Temperature (° C.) Pressure (bara)Stream 108 entering syngas heat recovery heat exchanger 109 PreferredAbove freezing point to below Relative to reforming pressure: conditionsstream 190 temperature 1.3 to 1 times Example ranges 0.1 to 350, 1 to250, 10 to 150, Relative to reforming pressure: of conditions 15 to 501.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to 1.03 time Stream 108leaving syngas heat recovery heat exchanger 109 Preferred 100 to 200Relative to reforming pressure: conditions 1.3 to 1 times Example ranges110 to 190, 120 to 180, 120 to 150, Relative to reforming pressure: ofconditions 120 to 140 1.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to 1.03time Stream 107, air feed stream entering syngas heat recovery heatexchanger 110 Preferred Above stream dew point to below Relative toatmospheric pressure: conditions stream 190 temperature 1.2 to 1 timesExample ranges −40 to 350, −10 to 250, 0 to 200, 10 Relative toreforming pressure: of conditions to 150, 15 to 50 1.2 to 1.01 times,1.15 to 1.01 times, 1.1 to 1.03 times Stream 107, air feed streamleaving syngas heat recovery heat exchanger 110 Preferred Relative tosyngas feed stream 190 Relative to atmospheric pressure: conditionstemperature: 1.2 to 1 times −20 to −100 Example ranges Relative tosyngas feed stream 190 Relative to atmospheric pressure: of conditionstemperature: 1.2 to 1.01 times, 1.15 to 1.01 times, 1.1 to −25 to −90,−25 to −50, 1.03 times −25 to −40 Stream 105, fuel feed stream enteringsyngas heat recovery heat exchanger 110 Preferred Above stream dew pointto below Relative to atmospheric pressure: conditions stream 190temperature 10 to 1.01 times Example ranges −40 to 350, −10 to 250, 0 to200, 10 Relative to atmospheric pressure: of conditions to 150, 15 to 508 to 1.01 times, 5 to 1.01 times, 1.2 to 1.01 times, 1.1 to 1.03 times

TABLE 8 Temperature and Pressure Properties of Some Process Streams ofan Embodiment According to FIG. 1 Temperature (° C.) Pressure (bara)Stream 118, air/fuel effluent from syngas heat recovery heat exchanger110 Preferred conditions Relative to syngas feed stream 190 Relative toatmospheric pressure: temperature: 10 to 1.01 times −20 to −100 Exampleranges of Relative to syngas feed stream 190 Relative to atmosphericpressure: conditions temperature: 8 to 1.01 times, 5 to 1.01 times, 1.2−25 to −90, −25 to −50, to 1.01 times, 1.1 to 1.03 times −25 to −40Stream 162 Preferred conditions 200 to 400 Relative to atmosphericpressure: 1.1 to 1 times Example ranges of 200 to 300, 220 to 280Relative to atmospheric pressure: conditions 1.05 to 1.001 times, 1.02to 1.001 times Stream 163 entering heat exchanger 164 Preferredconditions 300 to 500 Relative to atmospheric pressure: 1.1 to 1 timesExample ranges of 350 to 480, 380 to 440 Relative to atmosphericpressure: conditions 1.05 to 1.001 times, 1.02 to 1.001 times Stream 163leaving heat exchanger 164 Preferred conditions 120 to 200 Relative toatmospheric pressure: 1.1 to 1 times Example ranges of 130 to 190, 140to 160 Relative to atmospheric pressure: conditions 1.05 to 1.001 times,1.02 to 1 times Stream 108 leaving heat exchanger 164 Preferredconditions 120 to saturated steam temperature Relative to reformingpressure: 1.25 to 1 times Example ranges of 130 to saturated steamtemperature Relative to reforming pressure: conditions 150 to saturatedsteam temperature 1.1 to 1.001 times, 1.1 to 1.01 times, 180 tosaturated steam temperature 1.1 to 1.05 times Stream 172 Preferredconditions Saturated steam temperature Relative to reforming pressure:1.25 to 1 times Example ranges of Saturated steam temperature Relativeto reforming pressure: conditions 1.1 to 1.001 times, 1.1 to 1.01 times,1.1 to 1.05 times

FIG. 20-21 show front and rear perspective views of a partialconfiguration of an embodiment of a reformer system 700. The figureshave been simplified by removing portions of the piping. The embodimentshown corresponds to a system having the schematic of FIG. 7. As such,only air feed stream 107, combustion air stream 114, fuel stream 104,gaseous hydrocarbon stream 102 enter syngas heat recovery heat exchanger110 and water stream 108 enters heat exchanger 109, which is part ofsyngas heat recovery heat exchanger 110, to exchange heat with syngasstream 190 leaving water-gas shift reactor 186. Among the streams orpiping not shown is the split of the fuel/air mixture leaving syngasheat recovery heat exchanger 110 to feed fuel/air to the air streamleaving syngas heat recovery heat exchanger 110, prior to the streamsentering pre-heaters 120 and 122 as this occurs within the header 2010supplying pre-heater 120 in connection with the header 2015 forpre-heater 122. After being pre-heated in pre-heater 120, the fuelleaves the pre-heater as the reformer fuel stream and enters a fuelsupply header 2020 that spans the length of the reformer 820 andprovides for supply of the fuel to each of the individual fuel supplyflow access paths or chambers on the reformer stack. In this manner, thefuel may be supplied to each of the reformer stages in parallel and thesupply may be passively controlled by the configurations of theindividual fuel supply streams connecting to each combustion chamber inthe reformer. Because this embodiment corresponds to an embodimentaccording to FIG. 7, water stream 108 receives heat directly from fluegas stream 160 as it leaves the pre-reformer 800 with no pre-heating ofthe flue gas stream. After leaving heat exchanger 164, water stream 108proceeds to quench heat exchanger 165, where it receives heat from aportion of syngas stream 180 after it is split shortly after leavingreformer 820. As shown in FIG. 20-21, pre-reformer 800 and reformer 820each comprise PCRs that are stacked and diffusion bonded plates asdescribed with respect FIG. 9 and FIG. 11 respectively and then placedon their sides.

Also shown in FIG. 20-21, are gaseous hydrocarbon-steam header 2102 thatfeeds gaseous hydrocarbon-steam stream 174 to the gaseoushydrocarbon-steam channels on the gaseous hydrocarbon-steam plates ofreformer 800 and reformer stream header 2104 that collects the reformerstream 811 as it leaves pre-reformer 800 via the reformer streamchannels. From header 2104, reformer stream 811 connects to reformerstream header 2110 that feeds the reformer stream inlet channels of thebounding plates and reformer plates that are included in reformer 820.FIG. 20-21 also include syngas stream header 2106 that collects thereformed streams leaving the bounding plates and the reformer plates ofreformer 820 via the reformer stream outlet channels to form syngasstream 180. In FIG. 21, the combustion chamber and the reforming chambercreated by stacking the plates are shown capped off with penetrationcaps 2108, which may be connected, such as welded or otherwise connectedover the combustion chamber and the reforming chamber penetrations onthe endplate of the reformer 820.

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is intendedthat the following claims define embodiments of the scope of theinvention and that methods and structures within the scope of theseclaims and their equivalents be covered thereby.

What is claimed is:
 1. A gaseous hydrocarbon-steam reforming processcomprising: partially combusting the fuel in a first fuel/air mixturestream to heat the fuel/air mixture stream for use during reforming of agaseous hydrocarbon-steam stream; combusting a second fuel/air mixturestream to heat an air stream for use during reforming of the gaseoushydrocarbon-steam stream; and reforming the gaseous hydrocarbon-steamstream to form a syngas stream and a flue gas stream.
 2. The process ofclaim 1, further comprising: reducing metal dusting and/or coking duringthe reforming step by heating and pre-reforming the gaseoushydrocarbon-steam stream in multiple pre-reforming stages, prior toreforming the gaseous hydrocarbon-steam stream.
 3. The process accordingto claim 2, wherein heating comprises recovering heat from the flue gasstream into the gaseous hydrocarbon-steam stream in a heat exchanger. 4.The process of claim 1, wherein said reforming comprises at least threestages of: i) heating the gaseous hydrocarbon-steam stream by recoveringheat from the heated air stream to form a heated reformer stream and acooled air stream; ii) reforming at least a portion of the heatedreformer stream; and iii) combusting a portion of the partiallycombusted fuel/air mixture stream in the presence of the cooled airstream to re-heat the cooled air stream.
 5. The process of claim 4,wherein an amount of the fuel/air mixture supplied to the combustingstep of each of the at least three stages is passively controlled. 6.The process of claim 5, wherein said passive control is accomplished bybalancing pressure drops in the fuel and air lines throughout thegaseous hydrocarbon-steam reforming process.
 7. The process of claim 1,wherein said process has a hydrocarbon conversion of greater than 50%.8. The process of claim 1, wherein said process has an energy efficiencyof greater than 50%.
 9. The process of claim 1, wherein metal dustingand coking conditions are avoided within all heat exchangers,pre-reforming stages and reforming stages within the process.
 10. Agaseous hydrocarbon-steam reforming process comprising: a) preheatingone or more air streams to form one or more preheated air streams; b)combining at least one air stream with a portion of at least one fuelstream to form a fuel/air mixture having a temperature below metaldusting conditions; c) partially combusting the fuel in a portion of thefuel/air mixture to form a heated fuel stream having a temperature abovemetal dusting conditions for use in the reformer stages; d) combusting aportion of the fuel/air mixture in the presence of at least one of thepreheated air streams to form a heated air stream having a temperatureabove metal dusting conditions for use in the reformer stages; e)heating one or more water streams to form steam; f) mixing the steamwith one or more gaseous hydrocarbon streams to form a gaseoushydrocarbon-steam stream; g) heating and partially reforming the gaseoushydrocarbon-steam stream in one or more pre-reforming stages to form areformer stream, wherein throughout the one or more pre-reforming stagesthe gaseous hydrocarbon-steam stream has a combination of temperatureand composition that avoids metal dusting and coking conditions; h)reforming the reformer stream in one or more reformer stages to form asyngas stream and a flue gas stream, wherein throughout the one or morereforming stages the reformer stream has a combination of temperatureand composition that avoids metal dusting and coking conditions; i)recovering heat from the flue gas stream to provide heat to thepre-reforming stages in step g) and to provide preheating to the waterstream; and j) recovering heat from the syngas stream to preheat the airstream from step a) and to provide heat to form steam in step e). 11.The process according to claim 10, wherein each of said pre-reformingstages comprises: i) recovering heat from said flue gas stream to heatsaid gaseous hydrocarbon-steam stream; and ii) partially reforming theheated gaseous hydrocarbon-steam stream.
 12. The process according toclaim 10, wherein said reforming and re-heating the reformer stream inone or more reformer stages to form a syngas stream and a flue gasstream comprises multiple stages of: i) heating the reformer stream byrecovering heat from the heated air stream in a heat exchanger to form aheated reformer stream and a cooled air stream, ii) reforming at least aportion of the heated reformer stream; and iii) combusting a portion ofthe heated fuel stream in the presence of the cooled air stream to formthe heated air stream for the next stage.
 13. The process according toclaim 11, further comprising quenching at least a portion of the syngasstream in a quench heat exchanger.
 14. An apparatus for steam reformingof a gaseous hydrocarbon comprising: a) a fuel pre-heater that partiallycombusts the fuel in a first fuel/air mixture to form a heated fuelstream, the heated fuel stream being combusted in a reformer module; b)an air pre-heater that combusts a portion of a second fuel/air stream inthe presence of an air stream to form a heated air stream, the heatedair stream supplying heat to the reformer module; c) a reformer modulefor forming a syngas stream from a reformer stream.
 15. The apparatus ofclaim 14, wherein said reformer module comprises one or morepre-reformer stages and one or more reformer stages.
 16. The apparatusaccording to claim 15, wherein each of said pre-reformer stages comprisea heat exchanger and a catalyst chamber.
 17. The apparatus according toclaim 16, wherein said pre-reformer stages are configured to recoverheat via the heat exchanger from a flue gas stream leaving the reformermodule.
 18. The apparatus of claim 15, wherein said reformer stagescomprise: i) a heat exchanger that heats the reformer stream byrecovering heat from the heated air stream to form a cooled air stream;ii) a reforming bed that reforms the heated reformer stream; and iii) acombustion chamber that combusts a portion of the heated fuel stream tore-heat the cooled air stream.
 19. The apparatus of claim 18, whereinsaid apparatus includes a fuel distribution control network configuredfor passive control of the amount of the heated fuel stream supplied toeach combustion chamber in the reformer stages.
 20. The apparatusaccording to claim 14, wherein said apparatus further comprises at leastone heat exchanger that recovers heat from said syngas stream after itleaves the reformer module.
 21. The apparatus according to claim 20,wherein said at least one heat exchanger comprises at least one quenchheat exchanger that recovers heat from a portion of said syngas stream.22. The apparatus according to claim 20, where said at least one heatexchanger comprises a multi-stream heat exchanger.
 23. The apparatus ofclaim 14, wherein said apparatus is configured to avoid or reduce metaldusting and coking conditions within all heat exchangers, pre-reformingstages and reforming stages.
 24. The apparatus of claim 14, furthercomprising a water-gas shift reactor that increases the concentration ofhydrogen in the syngas stream after the syngas stream leaves thereformer module.
 25. An apparatus for steam reforming of a gaseoushydrocarbon comprising: a) a syngas heat recovery heat exchanger thatrecovers heat from a syngas stream to heat at least one air stream; b)an air flow splitter that splits the air stream into a first air streamand a second air stream, the first air stream connecting to a fuelstream to form a fuel/air mixture; c) a fuel flow splitter that splitsthe fuel/air mixture into a first fuel/air stream and a second fuel/airstream, the first fuel/air stream connecting to a fuel pre-heater andthe second fuel/air stream connecting to an air pre-heater; d) a fuelpre-heater that partially combusts the fuel in the first fuel/air streamto form a heated fuel stream for use in the reformer; e) an airpre-heater that combusts the second fuel/air stream in the presence ofthe second air stream to form a heated air stream for use in thereformer; f) a pre-reformer that partially reforms a heated gaseoushydrocarbon stream in the presence of steam to form a reformer stream;g) a reformer that reforms the reformer stream to form a syngas stream;h) a quench exchanger that recovers heat from the syngas stream to formsteam from a water stream for the pre-reformer.
 26. The apparatus ofclaim 25, wherein said pre-reformer comprises a printed circuit reactor.27. The apparatus according to claim 25, wherein said reformer comprisesa printed circuit reactor.